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Thermosensitive liposomes (TSL) have been used for localized temperature-responsive release of chemotherapeutics into solid cancers, with a minimum of one invention currently in clinical trials (phase III). In this study, TSL was designed using a lipid blend comprising 1,2-dipalmitoyl

Cyclophosphamide is a well-known anticancer agent acting by means of DNA alkylation. Associated with its tumor selectivity, it also possesses a wide spectrum of toxicities. As the requirement of metabolic activation before cyclophosphamide exerts either its therapeutic or toxic effects is well recognized, research aiming at elucidating the pathways that lead to the activation of this drug is of key importance. This has created the necessity for developing an effective analytical method for detecting cyclophosphamide and its breakdown products. In this paper, an Acquity TQ tandem quadrupole mass spectrometer equipped with electrospray ionization in positive-ion mode was employed for detecting cyclophosphamide in its protonated form. The full-scan mass spectrum of cyclophosphamide shows two ion clusters displaying the characteristic isotopic pattern of two chlorine atoms and assigned as sodiated cyclophosphamide, [CP + Na]

The dramatic rise in cancer incidence, alongside treatment deficiencies, has elevated cancer to the second-leading cause of death globally. The increasing morbidity and mortality of this disease can be traced back to a number of causes, including treatment-related side effects, drug resistance, inadequate curative treatment and tumor relapse. Recently, anti-cancer bioactive peptides (ACPs) have emerged as a potential therapeutic choice within the pharmaceutical arsenal due to their high penetration, specificity and fewer side effects. In this contribution, we present a general overview of the literature concerning the conformational structures, modes of action and membrane interaction mechanisms of ACPs, as well as provide recent examples of their successful employment as targeting ligands in cancer treatment. The use of ACPs as a diagnostic tool is summarized, and their advantages in these applications are highlighted. This review expounds on the main approaches for peptide synthesis along with their reconstruction and modification needed to enhance their therapeutic effect. Computational approaches that could predict therapeutic efficacy and suggest ACP candidates for experimental studies are discussed. Future research prospects in this rapidly expanding area are also offered.

Marine algae are a rich source of biologically active compounds that can be utilized in various food and pharmaceutical applications. In this study, ultrasound-assisted extraction (UAE) was optimized to maximize yield and total carbohydrate content extracted from the red algae, Pterocladia capillacea. The extract was shown to possess potent antioxidant activity of up to ~70%, and was successfully used as a reducing and capping agent in the green synthesis of copper nanoparticles, which were characterized by UV-spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and dynamic light scattering (DLS). Primarily, CuO nanoparticles with an average size of 62 nm were produced. FTIR spectra for the extract and algal-mediated CuO nanoparticles showed characteristic polysaccharide peaks. The synthesized CuO nanoparticles were subsequently loaded with nedaplatin where UV data suggested a complex formation. Nedaplatin release profiles showed a sustained release that reached a maximum at 120 h. The formulation was shown to have greater cytotoxicity relative to nedaplatin on hepatocellular carcinoma, breast cancer and ovarian cancer cell lines with IC50 values of 0.40 ± 0.08, 1.50 ± 0.12, and 0.70 ± 0.09 µg/mL, respectively. Loading nedaplatin onto CuO nanoparticles synthesized using red algae extract, greatly enhances its anticancer effect.

In this study, two environmentally-friendly macroscopically formal (PVF) composited sponges (PL and PLS) functionalized with lignin and lignosulfonate, respectively, were fabricated by a one-step mechanical foaming method. PLS possessed the largest specific surface area of approximately 22.396 m2/g, a three-dimensional skeleton structure with a skeletal density of 3.236 g/cm3, and 0.338 mmol/g of acidic oxygen-containing groups. Thus, it showed the highest adsorption capacity of 0.16–0.24 mmol/g (51.17–76.75 mg/g) in removing seven antibiotics, of the popular fluoroquinolones (FQs) family from water. The contributions of hydrogen bonding, electrostatic attraction (EA) and π-π electron donor-acceptor interaction to the adsorption of FQs onto the PL and PLS sponges were analyzed systematically by investigating the pH dependence of the adsorption capacity, and the changes in adsorption of two sub structural analogs of FQs as molecular probes, and by performing theoretical calculations. The EA between the acidic oxygen-containing groups on the sponges and the amino groups of FQs played a dominant role in adsorption in near neutral conditions, leading to a superior adsorption performance for PLS. Overall, the composited sponges have the advantages of simple production, environmental-friendliness, convenient recycle, and low cost, which renders them potentially viable in treating real wastewater containing FQs.

The preoxidation effects of H2O2, NaClO, and KMnO4 on the dewaterability of sewage sludge were compared by analyzing the changes in specific resistance to filtration (SRF), filter cake moisture content (FCMC), extracellular polymeric substance (EPS) fractions and components, and floc properties. The three oxidants varied in oxidation efficiency and exhibited distinctive mechanisms. NaClO not only destroyed sludge flocs and EPSs but also effectively caused cell lysis, resulting in release of a considerable amount of organic matters and subsequently significant deterioration of dewatering performance. The oxidation of H2O2 and KMnO4 was relatively mild and occurred mainly on the outer layers of the sludge flocs and cell-bound EPSs. By contrast, the SRF and FCMC of the sludge conditioned with a low dose of KMnO4 were slightly improved, and a fraction of soluble EPS was compressed because of the coagulation effect of the oxidation product MnO2. The pH of the sludge conditioned with H2O2 and KMnO4 showed no considerable change. Meanwhile, NaClO evidently increased the alkalinity of the sludge because of the hydrolysis effect. After the pH of the NaClO-treated sludge was readjusted to 7.0, the partial protonation efficiency slightly alleviated the deterioration of sludge dewatering performance. The preoxidized sludge was then subjected to reflocculation treatment using FeCl3, polyacrylamide, and a cationic starch-based flocculant, respectively. The combined treatment of preoxidation and reflocculation showed a high dewatering efficiency owing to their synergistic effect.

Choline is a quaternary ammonium bioactive compound that is used as a dietary supplement. Direct determination of choline in pharmaceutical formulations is a challenging analytical task. The strong UV absorbance of p-sulfonatocalix[4]arene (SC4) and its outstanding complexation properties towards quaternary ammonium compounds have been utilized to develop a method to detect and quantify choline in aqueous solution. This method has been applied to a commercial pharmaceutical choline formulation showing results with no statistically significant difference from those obtained by the official U.S. Pharmacopeial method. The method was validated according to ICH guidelines and the limit of detection for choline was calculated to be 7.2 × 10−6 mol L−1 (1.30 μg mL−1). The host-guest complexation between SC4 and choline were investigated using UV and 1H NMR spectroscopy and DFT calculations. The peak amplitude of the host-guest complexes formed were found to be linearly proportional to the concentration of the choline and l -carnitine analytes in the ranges of 1.0 × 10−5 to 1.6 × 10−4 mol L−1 and 1.0 × 10−5 to 1.8 × 10−4 mol L−1 respectively. The reaction stoichiometry between either choline or l -carnitine with SC4 in the formed complexes were determined to be 1:1 while the stability constants for the complexes formed were estimated to be 8.3 × 104 M−1 and 2.8 × 104 M−1 in the case of choline and l -carnitine, respectively. Both 1H NMR spectroscopy and DFT calculations suggest the complexation between choline and SC4 involves the insertion of the trimethylammonium group of choline into the cavity of SC4 in agreement with previously published X-ray data. The spectrophotometric method presented here should not be limited to the determination of choline. The linear relationship between the peak amplitude of the host-guest complex formed between SC4 and l -carnitine presented here suggests the applicability of the method for the detection of other small molecular species possessing a quaternary ammonium group.

Fava bean peels, Vicia faba (FBP) are investigated as biosorbents for the removal of Methylene Blue (MB) dye from aqueous solutions through a novel and efficient sorption process utilizing ultrasonic-assisted (US) shaking. Ultrasonication remarkably enhanced sorption rate relative to conventional (CV) shaking, while maintaining the same sorption capacity. Ultrasonic sorption rate amounted to four times higher than its conventional counterpart at 3.6 mg/L initial dye concentration, 5 g/L adsorbent dose, and pH 5.8. Under the same adsorbent dose and pH conditions, percent removal ranged between 70–80% at the low dye concentration range (3.6–25 mg/L) and reached about 90% at 50 mg/L of the initial dye concentration. According to the Langmuir model, maximum sorption capacity was estimated to be 140 mg/g. A multiple linear regression statistical model revealed that adsorption was significantly affected by initial concentration, adsorbent dose and time. FBP could be successfully utilized as a low-cost biosorbent for the removal of MB from wastewater via US biosorption as an alternative to CV sorption. US biosorption yields the same sorption capacities as CV biosorption, but with significant reduction in operational times.

Macromolecules including macrocyclic species have been reported to have the potential to encapsulate biologically active compounds such as drugs through host-guest complexation to increase their solubility, stability and bioavailability. In this paper the first experimental and theoretical investigation of the complexation between nedaplatin, a second generation antineoplastic drug, and p-4-sulfocalix[4]arene, a macromolecule possessing a bipolar amphiphilic structure with good biocompatibility and relatively low haemolytic toxicity for potential use as a drug delivery system is presented. Data from 1H NMR, UV, Job's plot analysis, HPLC and DFT calculations are detailed and suggest the formation of a 1:1 complex. The stability constant of the complex was experimentally estimated to be 3.6 × 104 M− 1 and 2.1 × 104 M− 1 which correspond to values of − 6.2 and − 5.9 kcal mol− 1, respectively for the free energy of complexation while the interaction free energy is calculated to be − 4.9 kcal mol− 1. The formed species is shown to be stabilised in solution through hydrogen bonding between the host and the guest which may allow for this strategy to be effective for potential use in drug delivery.

The occurrence and concentrations of six common phthalates were investigated for the first time in bottled water locally produced in the Egyptian market. The compounds investigated were dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), n-butyl benzyl phthalate (BBP), diethyl hexyl phthalate (DEHP), and Di-n-octyl phthalate (D-n-OP). A set of 108 bottled water samples from six different commercial brands of water bottled in transparent polyethylene terephthalate (PET) plastic bottles with high density polyethylene (HDPE) plastic caps were investigated. Water samples were analyzed immediately after purchasing (~2weeks after production), after being stored at room temperature (25±5°C), in a refrigerator (4±1°C) and outdoor under sun exposure (daylight temperature of 40±5°C). Samples were stored up to six months depending on the tested condition. Among the target compounds, only DEHP and DBP were detected in the samples analyzed immediately after purchasing with a detection frequency of 50 and 58% and mean concentrations of 0.104 and 0.082μgl-1 respectively. Significant positive correlation was obtained between the storage time, temperature and the concentration of phthalate compounds detected in the bottled water, indicating possible migration from the PET plastic material as the source. The estimated contribution of bottled water consumption to the tolerable daily intake (TDI) levels of the two most abundant phthalates observed here for adults and toddlers did not exceed 0.16 and 0.72% for DBP while these values were 0.04 and 0.16% for DEHP respectively. These estimated daily intake values from PET bottled water consumption were far below their respective TDI values and therefore should constitute no adverse health effects.

l

The preoxidation effects of H

Choline (Ch+), is a vitamin-like essential water-soluble organic micronutrient. The US-FDA requires that infant formula not made from cow's milk must be supplemented with Ch+. Direct determination of Ch+ in milk powders and infant formulas is a challenging task due to the lack of a detectable chromophore, its existence in free and complexed forms as well as the presence of multi-analytes in these complex matrices. Here, an enzyme-free potentiometric ion selective electrode (ISE) with high selectivity for Ch+, a linear range from 0.03 μM up to 1 mM, a 0.061 μM detection limit (LOD) and a typical response time less than 5 and no greater than 60 s is developed for monitoring of Ch+ in infant formula and milk powders. To achieve these ISE parameters we relied on the ability of calixarenes and its derivatives to form host-guest complexes with the positively charged quaternary ammonium moiety of Ch+. We employed a lipophilic (membrane-compatible) calixarene as an ionophore in the sensing membrane phase to provide a molecular receptor for Ch+ capable of selective binding; while utilizing, hydrophilic (water-soluble) p-sulfonated calixarene as a buffering agent to optimize the inner filling solution to reduce transmembrane Ch+ fluxes. All the calixarene structures and their complexes with Ch+ were optimized at the density functional theory (DFT) level and the Gibbs free energies for the inclusion of Ch+ into the calixarenes were calculated. The prepared sensor was shown to selectively respond only to Ch+ in the presence of all other interferents in the tested matrices with results that are not statistically significantly different for either accuracy or precision relative to the much more laborious official AOAC 1999 coupled enzymatic–spectrophotometric method. The proposed method is highly selective, non-enzymatic, requires no derivatization or incubation steps, offers a fast response time, and has the potential of portability for in situ analysis, while being relatively cost effective and non-laborious.

Following the discovery of cisplatin over 50 years ago, platinum-based drugs have been a widely used and effective form of cancer therapy, primarily causing cell death by inducing DNA damage and triggering apoptosis. However, the dose-limiting toxicity of these drugs has led to the development of second and third generation platinum-based drugs that maintain the cytotoxicity of cisplatin but have a more acceptable side-effect profile. In addition to the creation of new analogs, tumor delivery systems such as liposome encapsulated platinum drugs have been developed and are currently in clinical trials. In this study, we have created the first PEGylated liposomal form of nedaplatin using thin film hydration. Nedaplatin, the main focus of this study, has been exclusively used in Japan for the treatment of non-small cell lung cancer, head and neck, esophageal, bladder, ovarian and cervical cancer. Here, we investigate the cytotoxic and genotoxic effects of free and liposomal nedaplatin on the human non-small cell lung cancer cell line A549 and human osteosarcoma cell line U2OS. We use a variety of assays including ICP MS and the highly sensitive histone H2AX assay to assess drug internalization and to quantify DNA damage induction. Strikingly, we show that by encapsulating nedaplatin in PEGylated liposomes, the platinum uptake cytotoxicity and genotoxicity of nedaplatin was significantly enhanced in both cancer cell lines. Moreover, the enhanced platinum uptake as well as the cytotoxic/antiproliferative effect of liposomal nedaplatin appears to be selective to cancer cells as it was not observed on two noncancer cell lines. This is the first study to develop PEGylated liposomal nedaplatin and to demonstrate the superior cell delivery potential of this product.

Organophosphate esters (OPEs) are commonly used as flame retardants (FRs) and plasticizers. The usage of OPEs has increased recently due to the ban of several brominated flame retardants, but information on levels in the environment, including the indoor environment is still limited. We investigated the occurrence and distribution of 12 OPEs in urban house dust from Vancouver, Canada; Istanbul, Turkey; and Cairo, Egypt. The medianSOPE concentration was 41.4 mu g/g in the Vancouver samples while median levels in Istanbul and Cairo were significantly lower. The median composition profiles of OPEs in Vancouver and Cairo were dominated by tris (2-butoxyethyl) phosphate (TBOEP), accounting for 56 and 92% of total OPEs respectively while it showed a detection frequency of only 14% in Istanbul. Tris (2-chloropropyl) phosphate (TCPP) was the most abundant chlorinated OPE representing 20 and 36% of the total OPEs in Vancouver and Istanbul respectively, but was below the detection limit in the Cairo dust samples. Consistent with other studies, SOPE concentrations were similar to 1 to 2 orders of magnitude higher than PBDEs and currently used flame retardants in the same dust samples. The mean estimated daily intakes (EDI) of SOPE from dust were 115, 38 and 9 ng/kg/bw/day in Vancouver, Cairo and Istanbul respectively for toddlers where adults were similar to 10 times lower. The total toddler OPE intake ranged from 115 to 2900, 38 to 845 and from9 to 240 ng/kg bw/day across the three cities. TBOEP had the largest contribution to the EDI in both toddler and adults, where toddler TBOEP exposures via dust represented 4% to 80%, 2% to 44% and 0.1% to 6% of the Reference Doses (RfD) in the mean and high intake scenarios for toddlers in Vancouver, Cairo and Istanbul respectively. Crown Copyright (C) 2018 Published by Elsevier B.V. All rights reserved.

There are very few studies reporting concentrations of polybrominated diphenyl ethers (PBDEs) and novel flame retardants (FRs) or non-PBDEs in Africa and the Middle East. The present work reported concentrations of fourteen PBDE congeners and eleven non-PBDE flame retardants in dust samples collected from homes (n=17), workplaces (n=9) and cars (n=5) in the greater Cairo region. The median ∑PBDE concentrations were 57, 425 and 1608 ng g(-1) in homes, workplaces and cars respectively. The highest PBDE levels were observed for BDE 209, with a median concentration of 40.2, 366 and 1540 ng g(-1) representing 70% to 95% of the total PBDEs in homes, workplaces and cars respectively. This is about 8 to 46 times greater than the median concentration of the pentaBDE (represented by the most abundant compounds in this formulation, ∑BDE 47, 99 and 100). In the case of non-PBDE flame retardants, a detection frequency between 52% and 100% was observed for several compounds including: hexabromocyclododecane (HBCD), hexabromobenzene (HBB), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB), bis (2-ethyl-1-hexyl) tetrabromophthalate (TBPH), 1,2-bis (2,4,6-tribromophenoxy) ethane (TBPE), ally-2,4,6-tribromophenyl ether (ATE) and Dechlorane Plus (DP). The ∑non-PBDE median concentrations were 8.30, 28.9 and 49.9 ng g(-1) in homes, workplaces and cars respectively with the highest level observed for HBCD in the three microenvironments. The detection of novel flame retardants in indoor environments may be due to their wide usage after the ban of the penta and octa BDE formulation. Results show the levels of PBDEs and non-PBDEs in Egyptian dust to be among the lowest levels reported from other countries. Different dust exposure scenarios using 5th percentile, median, 95th percentile and maximum levels were estimated for adult and children. The estimated dust intake results were several orders of magnitude lower than the oral reference dose values.

For the synthesis and selection of active platinum-based anticancer drugs that perform better than cisplatin and its analogues, six-coordinate octahedral Pt(IV) complexes appear to be promising candidates as, being kinetically more inert and more resistant to ligand substitution than four-coordinate Pt(II) centers, they are able to minimize unwanted side reactions with biomolecules prior to DNA binding. Due to their kinetic inertness, Pt(IV) complexes have also been exploited to bypass inconvenient intravenous administration. The most prominent example is satraplatin (Sat.) which is the first platinum antineoplastic agent reported to have oral activity. The present paper deals with a theoretical DFT investigation of the influence that the acidity of the biological environment can have on the activity of satraplatin and analogous octahedral Pt(IV) complexes having two carboxylates as axial ligands. Moreover, here the outcomes of a joint electrospray ionization mass spectrometry and DFT investigation of the fragmentation pathways of the protonated satraplatin are reported. Calculations show that the simulated acidic environment has an important impact on the satraplatin reactivity causing a significant lowering of the barrier that is necessary to overcome for the hydrolysis of the first acetate ligand to occur. Data from electrospray ionization mass spectrometry

Pt-based anti-cancer drugs can form complexes with biological ligands other than their intended pharmacological targets. Such complexes are believed to be a major contributor to the reduction of the anti-cancer drugs’ therapeutic potential and can act as potential causes of toxicity. Recently, the cytoplasmic ligand β - alanyl-L-histidine dipeptide (carnosine) was shown to act as a sequestering agent for oxaliplatin (OxPt) inhibiting its cytotoxic action most likely through the formation of complexes that are less cytotoxic than OxPt alone. In this paper, the calculated binding modes and binding energies of protonated carnosine as well as canosine complexes with various biologically relevant metal cations and some common Pt-based anti-cancer drugs both in the gas phase and in solution are presented. Theoretical evidence for the existence of protonated carnosine in a zwitterionic form is offered. Six calculated geometrical arrangements comprising general structural motifs of metal ion-carnosine complexes are presented. In all but one of these six conformers the metal ions were shown to form three bonds to each of the carnosine ligands. These six general binding motifs were found to cover the lowest energy structures of all species investigated here whether in the gas phase or in solution. The data presented increases our knowledge of the interactions of carnosine with different metals, either those naturally found inside the body or those that are up taken via foods, supplements or drugs.

Macromolecules including macrocyclic species have been reported to have the potential to encapsulate biologically active compounds such as drugs through host-guest complexation to increase their solubility, stability and bioavailability. Here we investigate the complexation between nedaplatin, a second generation antineoplastic drug, and p-4-sulfocalix[4]arene, a macromolecule possessing a bipolar amphiphilic structure with good biocompatibility and relatively low haemolytic toxicity for potential use as a drug delivery system. Data from 1H NMR, UV-Vis spectroscopy, Job’s plot analysis, HPLC, DSC and DFT calculations are detailed and suggest the formation of a 1:1 complex. The stability constant of the complex was experimentally estimated to be 3.6 × 104 M−1 and 2.1 × 104 M−1 which correspond to values of −6.2 and −5.9 kcal mol−1, respectively for the free energy of complexation while the interaction free energy is calculated to be −4.9 kcal mol−1. The formed species is shown to be stabilised in solution through hydrogen bonding between the host and the guest. The complex displayed enhanced antitumor activity against MDA-MB-231 cells compared to nedaplatin which may allow for its application in cancer therapy.

A detailed structural analysis of the complexes resulting from the association of the neutral, mono- and di-anionic forms cytoplasmic thiol containing tripeptide glutathione (GSH) to the post water substituted hydrolysed form of the anti-cancer drug cisplatin, [Pt(NH 3 ) 2 ] 2+ , in the gas phase and in solution is presented. These structures which are formed from a 1:1 molar ratio of the glutathione ligand and the Pt-drug, have been proposed as possible intermediates for several postulated disulfide bridged polymeric species. Ten gas phase structures on the [GSH − H + Pt(NH 3 ) 2 ] + potential energy surface are presented and the coordination of the Pt metal is discussed. The [GSH + Pt(NH 3 ) 2 ] 2+ potential energy surface was also explored and twelve gas phase structures on this surface are presented. In order to describe the complexes examined here in solution, water solvation effects were considered for eight and nine of the most energetically favored structures of the [GSH − H + Pt(NH 3 ) 2 ] + and [GSH + Pt(NH 3 ) 2 ] 2+ potential energy surfaces, respectively. The enthalpy and free energy, based on the most thermodynamically favored conformers of the reactants and products, for the addition reaction [Pt(NH 3 ) 2 ] 2+ + [GSH − H] − → [GSH − H + Pt(NH 3 ) 2 ] + in the gas phase at 298 K were determined to be −331.8 and −314.8 kcal mol −1 , respectively. Similarly, the enthalpy and free energy of the gas phase reaction [Pt(NH 3 ) 2 ] 2+ + GSH → [GSH + Pt(NH 3 ) 2 ] 2+ at 298 K were determined to be −185.0 and −167.4 kcal mol −1 .

Protein phosphorylation and de-phosphorylation, provide one of the most common signalling pathways within cells, being involved in regulating cellular processes, mediating enzyme inhibition, protein–protein recognition and protein degradation. Compared with normal proteomics, phosphoproteomics poses some additional challenges requiring more initial separation and additional sensitivity to detect and quantify potentially ultra-low abundance species. In this work, the selective detection of phosphopeptides is described based on the incorporation of a metal tag, gallium–N,N-biscarboxymethyl lysine (Ga-LysNTA), in solution before separation and detection by liquid chromatography coupled to inductively coupled plasma mass spectrometry (LC–ICP-MS). Experimental and theoretical characterisation of the resulting Ga–phosphopeptide complex is presented based on linear ion trap electrospray ionisation mass spectrometry (ESI-MS), Fourier transform mass spectrometry (FT-MS) and molecular modelling data. Linear ion trap electrospray ionisation mass spectrometry (ESI-MS) was employed to study the interaction of the gallium tag with platelet derived growth factor beta receptor (s-PDGF), a small phosphopeptide. In addition high resolution Fourier transform mass spectrometry (FT-MS) was used for accurate mass determination and multistage tandem mass spectrometry of the gallium–s-PDGF complex identified the fragmentation pathway. Finally, molecular modelling was used to investigate the energetically favoured structures of both the Ga-LysNTA material and the s-PDGF–Ga-LysNTA complex.

The fragmentations of [AA + M](+) complexes, where AA = Phe, Tyr, Trp, or His, and M is a monovalent metal (Li, Na, or Ag), have been exhaustively studied through collision-induced dissociation (CID) and through deuterium labeling. Dissociations of the Li- and Ag-containing complexes gave a large number of fragment ions; by contrast, the sodium/amino acid complexes have lower binding energies, and dissociation resulted in much simpler spectra, with loss of the entire ligand dominating. Unambiguous assignments of these fragment ions were made and formation mechanisms are proposed. Of particular interest are fragmentations in which the charge was retained on the organic fragment and the metal was lost, either as a metal hydride (AgH) or hydroxide (LiOH) or as the silver atom (Ag(•)).

This paper describes methodologies, based on sector field inductively-coupled plasma mass spectrometry (SF-ICP-MS), and their application in the holistic study of the fate of Pt in human cell populations following treatment with cis- or oxaliplatin and combination treatments. Pt–DNA adduct formation data at several time points has been determined in the leukocytes from patients undergoing Pt-based chemotherapy demonstrating significant inter-patient variability and excellent reproducibility of the assay. The sensitivity of the technique enabled quantitation of as little as 0.2 Pt adducts per 10 6 nucleotides using 10 μg of patient DNA. Further, the first ever reported in vivo sub-cellular Pt fractionation data on a patient sample is presented indicating the feasibility of applying the methods presented here in a clinical environment. For in vitro studies, three cell models were used: A549 human lung adenocarcinoma epithelial cells were exposed to 50 μM cisplatin for 1 h; HCA7 human colorectal cancer cells were treated with either FOLFOX (200 μM 5-fluorouracil, 200 μM folinic acid and 50 μM oxaliplatin) or 50 μM oxaliplatin; and HT29 human colorectal cancer cells were treated with 50 μM oxaliplatin in combination with 20 μM methaneseleninic acid, CH 3 SeO 2 H (MSA). The cells were harvested and either the DNA extracted and/or a commercially available kit used to fractionate the treated cells into four sub-cellular compartments. Each of the sub-cellular fractions and extracted DNA were digested separately, evaporated to dryness and reconstituted in 2% nitric acid for analysis by SF-ICP-MS. The sub-cellular Pt distribution for cisplatin treated A549 cells was shown to be as follows: ∼70% localized in the cytosol, ∼17% in the membrane and membrane localized fraction, ∼9% in the nuclear fraction and ∼4% in the cytoskeletal fraction. Both FOLFOX and oxaliplatin treated HCA7 cells showed comparable sub-cellular Pt distributions, and Pt–DNA adduct formation was similar for the oxaliplatin and FOLFOX treatments with adduct yields of 5.6 and 5.5 adducts per 10 6 nucleotides respectively. It was found that the combination of oxaliplatin with 20 μM MSA did not change the distribution of Pt or significantly alter its accumulation in the cytosol of the HT29 cells. Mass balance experiments showed a >99% recovery of the total Pt in the sub-cellular fractions. These experiments are the first to provide such a detailed quantitation of Pt-drug partitioning and they show that the Pt broadly follows the total protein content of the individual compartments with the majority being scavenged in the cytosol compartment.

Positive mode electrospray mass spectrometry was used to investigate complexes of cysteine and selenocysteine with the metallo-drug Auranofin and the analogous chlorotriethylphosphine gold. Evidence for all the complexes, with the exception of the Auranofin–selenocysteine complex, was obtained. Several fragmentation products were examined and their proposed structures reported. Structural details of many experimentally observed ions including [Auranofin + H] + , [(CH 3 CH 2 ) 3 P–Au–cysteine] + and [(CH 3 CH 2 ) 3 P–Au–methylselenocysteine] + were examined by means of hybrid density functional theory at the B3LYP/DZVP level. Structural information and relative free energies are presented for several isomers of each ion considered.

The complexes of Ag + with the peptides MetGly, ProGly, GlyPro, GlyHis and GlyProAla were investigated using hybrid density functional theory at the B3LYP/DZVP level. The silver ion binding free energies at 298 K to each of these peptides was calculated to be 60.8, 52.0, 54.3, 71.2 and 63.3 kcal mol −1 , respectively. Structural information and relative free energies are presented for several isomers for each of the five complexes. Each of the global minima found for the five complexes is a charge-solvated ion. An important finding is that the Ag + –ProGly is the only complex where a salt bridge structure is energetically favored occurring at 4.0 kcal mol −1 higher in free energy than the global minimum. The Ag + ion in this salt bridge structure is attached to the carboxylate anion of zwitterionic ProGly in which the terminal amino nitrogen is protonated. For all the other complexes studied, the salt bridge structure occurs at much higher energies. All the dipeptide complexes with Ag + , but one, exhibit a di- or tri-coordinate metal where the sites of attachment are amino and carbonyl groups. However, the highest coordination numbers are not always the global minima due to steric costs. The global minimum of the Ag + –GlyProAla complex is the only structure found in this study where the metal is tetra-coordinated, binding to the terminal amino nitrogen and all three carbonyl oxygen atoms. Silver binding to sulphur and imidazole nitrogen atoms of MetGly and GlyHis, respectively, are present in the three most energetically favored species in each of these cases.

This paper presents size exclusion chromatography data with on-line coupling to UV and inductively coupled plasma mass spectrometry (ICP-MS) of water soluble metal-binding compounds present in zinc, copper, chromium and iodine enriched yeast nutritional supplements. Molecular weight estimates of the extracted metal-containing compounds are given and are shown to vary substantially from 1.2 kDa to larger than 668 kDa. Seven proteins suspected of containing chromium were identified from one of the chromium-containing fractions. Four of these identified proteins are known to form complexes with other metal ions. The metal chromatographic profiles of zinc, copper and chromium-enriched yeasts were compared to their respective native metal profiles in non-enriched yeast samples. The chromium profiles are shown to be markedly different while those of zinc and copper are qualitatively similar. Only iodide ions or weakly bound, non-aromatic, low molecular weight (∼ 1.2 kDa) iodine species were observed in the iodine-enriched yeast samples.

PFASs concentrations in dust samples collected from three microenvironments in Cairo ranged from 1.3 to 69 ng g(-1) with FTOHs being dominant. The 8:2 FTOH was detected in all samples. Among the FOSAs and FOSEs the MeFOSE was dominant while among ionic PFASs, PFOS and PFOA were most prominent. The concentrations of PFASs were among the lowest worldwide. Correlations between worldwide concentrations of PFOS + PFOA and country development indexes highlight higher usage and human exposure in more developed countries. Food packaging was analyzed for PFSAs, PFCAs and PAPs. The 6:2 and 8:2 monoPAPs were found to be above the MDL in 18% of the samples. PFOA was detected in 79% of the samples with median concentration of 2.40 ng g(-1). PFOS was detected in 58% of the samples with median concentration of 0.29 ng g(-1) while PFHxS and PFDS were below detection limit. Different human exposure scenarios were estimated.

The gas-phase dissociation chemistries of protonated 3-iodo- l -tyrosine, 3,5-diiodo- l -tyrosine and 3,3′,5,5′-tetraiodo-thyronine (thyroxine) have been examined using a combination of tandem mass spectrometry and density functional theory (DFT) calculations. It was found that, at low collision energy, all protonated tyrosines exhibit common fragmentation pathways, including the competitive eliminations of NH3 and the concomitant loss of H2O and CO, but there are significant differences in relative abundances, depending on the combined electron-donating abilities of the substituents in the phenyl ring. The ions initially formed by loss of NH3 are phenonium ions, but subsequent fragmentation is most easily understood in terms of the isomeric benzyl cation structures. These [M + H − NH3]+ ions fragment at relatively low collision energies, mainly by loss of ketene; by contrast, the [M + H − H2O − CO]+ ions are more stable towards dissociation. At higher collision energies, losses of one, two and even three iodine atoms were observed. DFT calculations (at the B3LYP/DZVP level of theory) were performed on protonated 3-iodotyrosine to compare the reaction profiles for the fragmentation mechanisms. The iodo-substituent in the 3-position is weakly electron-withdrawing and this results in a barrier (27.5 kcal/mol at 0 K) that is slightly higher than that for protonated tyrosine (26.8 kcal/mol). The phenoxy group PhO– is a weaker electron-donor than HO– and protonated 3,5-diiodo-4-phenoxytyrosine has an even higher barrier (31.1 kcal/mol) to NH3 loss than protonated 3,5-diiodotyrosine (28.8 kcal/mol). Linear free energy plots for Δ H 0 ° ‡ and Δ G 298 ° ‡ against σ+ for the four protonated tyrosine derivatives show good correlations. More importantly, as the products of the dissociation are higher in energy than the transition states to their formation, the plots of Δ H 0 ° and Δ G 298 ° for the overall reaction for NH3 loss also correlate very well with σ+ (correlation coefficients of 0.99 and 0.98, respectively). The positive slopes of these Hammett plots show that the barriers to the loss of NH3 by the neighboring-group mechanism are increased by the presence of electron-withdrawing groups in the phenyl rings.

Collision-induced dissociation of complexes, Ag+/NH2CH2(CH2) nCH2NH2, where n has values of 0, 1, 2 and 3, show loss of one H2 molecule at low energies. For the largest complex ( n = 3), a second H2 molecule is also lost. For complexes with n = 0 and 1, loss of AgH (the only pathway observed in the fragmentation of Ag+/monoamine complexes) also occurs at low collision energies and this becomes the dominant fragmentation pathway at centre-of-mass energies above 2 eV. For complexes with n = 2 and 3, negligible amounts of product ions resulting from loss of only AgH were formed. However, for these complexes, the major products at higher collision energies result from loss of either AgH plus NH3 or, more likely, H2 plus AgNH2; the product ions are postulated to be cyclic iminium ions. Density functional theory (DFT) calculations (B3LYP with a DZVP basis set) on Ag+/NH2CH2(CH2)2CH2NH2 showed the loss of H2 followed by AgNH2 to have a slightly lower barrier than loss of AgH plus NH3. For complexes with n = 2 and 3, there are minor losses of various combinations of AgH, H2, 2H2 and NH3. Reaction profiles for the losses of H2 and AgH from all four Ag+/α,ω-diamine complexes have been examined computationally using DFT calculations. The second step on the reaction profile, loss of either H2 or AgH from the complex between Ag+ and α-amino-γ-imino-propane, Ag+/NH2CH2CH2CHNH, has also been calculated. The highest energy transition state on the profiles to loss of both H2 and AgH from the smallest complex ( n = 0) are identical; on all the other profiles, the barrier for H2 loss is lower than that for AgH loss (by 2.5 kJ mol−1 when n = 1, by 13.4 kJ mol−1 when n = 2 and by 33.0 kJ mol−1 when n = 3). Fragmentation of the ligand backbone occurs most extensively for ions derived from the Ag+/NH2CH2CH2CH2NH2. After loss of H2, the product ion, Ag+/NH2CH2CH2CH = NH fragments via a transition state in which the CH2–CH2 bond is breaking, while a 1,5-hydrogen shift from one nitrogen to the other is occurring. Cleavage of the carbon chain of NH2CH2CH2CH = NH2+ occurs at relatively low energy; DFT calculations provide a mechanism by which H2C = NH plus CH3CH = NH2+ are produced.

The room-temperature reactivities of complexes of Cu + and Ag + with glycine have been investigated using an inductively coupled plasma-selected ion flow tube (ICP-SIFT)/multicollision-induced dissociation (CID) tandem mass spectrometer. These complexes were produced in a flow tube, collisionally thermalized and then allowed to react with CO, D 2 O or NH 3 . The measured reactivities of the CuGly + and AgGly + complexes have been compared with those of the bare metal cations towards the same neutral reagents. All observed reactions resulted in adduct formation, with helium buffer gas presumably acting as a stabilizing agent. Reaction rate enhancements of up to three orders of magnitude and lower extents of ligation were the main characteristics of the reactions initiated by the metal cation–glycine adducts as compared with those initiated by the bare metal cations. The kinetic information combined with equilibrium analyses and CID results suggest that, irrespective of the reagent, ligation to CuGly + is stronger than to AgGly + and, in both instances, ligation of carbon monoxide and water has comparable strengths, while much stronger coordination is achieved with ammonia. The structures of the complexes have been investigated computationally using density functional theory (DFT) at the B3LYP level employing the DZVP basis set. Optimized structures and the free energy changes associated with ligation have been computed. A good correlation was obtained between the experimental reaction efficiencies and the calculated free energies of bonding. Also, results are presented for the potential energy surfaces for the conversion of the “charge solvated” forms into the “metal salt” forms of CuGly + and AgGly + and of their adducts with CO or NH 3 . The computations indicate a modest catalytic effect of the CO and NH 3 on this conversion.

The binding energies at 0 K of sodium and silver ions to ammonia, methylamine, ethylamine, acetonitrile, and benzonitrile were determined using threshold collision-induced dissociation (CID) and molecular orbital calculations at the ab initio and density functional theory levels. There is good agreement between experimental and calculated binding energies. For the five ligands, threshold CID/CCSD(t)(fu)/6-311++G(2df,p)//MP2(fu)/6-311++G(d,p) Na+ binding energies are the following: ammonia, 25.6 ± 2.8/24.8; methylamine, 27.0 ± 1.4/25.9; ethylamine, 27.7 ± 2.3/27.1; acetonitrile, 30.0 ± 2.3/30.3; and benzonitrile, 32.7 ± 1.4/35.0 (B3LYP/6-311++G(d,p)//B3LYP/6-311++G(d,p)) kcal/mol. Threshold CID and B3LYP/DZVP Ag+ binding energies are the following: ammonia, 40.6 ± 3.0/38.9; methylamine, 41.5 ± 2.3/41.1; ethylamine, 42.9 ± 1.4/43.2; acetonitrile, 40.8 ± 2.0/39.3; and benzonitrile, 41.5 ± 2.8/43.1 kcal/mol. Wherever comparisons with literature data are possible, the Na+ binding energies determined in this ...

A hybrid quantum mechanical molecular mechanical (QMMM) approach is used to study H3O+, H2O, NH4+, NH3, Cl−, HCl, F−, HF, CH3COO−, CH3COOH, Ag+ and glycine in both zwitterionic and nonzwitterionic forms in water. The free energies of hydration of these species are presented and are shown to compare favorably with experimental values. The difference in water–glycine interaction energy between the zwitterionic and nonzwitterionic forms is calculated as a lower limit and is in line with previous findings. The first theoretical examination of the Ag+–glycine complex in solution is presented.

The complexes of silver ion, Ag+, with the twenty naturally occurring amino acids have been calculated using hybrid density functional theory at the B3LYP/DZVP level. For all of these silver complexes, several possible structures were examined, but as there are remarkable similarities between all the structures at the global minima, only summarized data are reported. All of the complexes, except that with proline, are solvated ions. Amino acids containing only hydrocarbon side chains are bidentate, coordinating through the amino and carbonyl groups and the remaining amino acids (with the exception of proline) are tricoordinate with the same two interactions as in the simpler amino acids and an additional interaction through the side chain. The proline complex contains zwitterionic proline with the Ag+ ion attached to the carboxylate anion. Enthalpies (at 298 K) for dissociation of Ag+ from the complexes range from 49.3 kcal mol-1 for glycine to 80.4 kcal mol-1 for arginine. Free energies for these reactio...

The binding enthalpies at 0 K of the silver ion to water, methanol, ethanol, diethyl ether, and acetone were calculated using density functional theory (DFT) using the hybrid B3LYP level of theory with the DZVP basis set; they were also measured using the threshold collision-induced dissociation (CID) method. There is good agreement between the two sets of data. For the five ligands, the DFT/threshold CID values are: water, 28.1/31.6 ± 2.5; methanol, 30.1/33.0 ± 3.7; ethanol, 32.0/33.9 ± 3.5; diethyl ether, 33.3/33.2 ± 1.5; and acetone, 36.2/38.0 ± 1.4 kcal/mol. The average of the absolute differences between the DFT and threshold CID results is 2.0 kcal/mol, a value smaller than the average experimental uncertainty of 2.5 kcal/mol. For identical ligands, the silver ion binding energies are lower than the lithium ion binding energies, but higher than the sodium ion binding energies.

Gas-phase collision-induced dissociation of the Ag+-proline complex shows six major product ions. Tandem mass spectrometry reveals that at least three of the fragment ions are formed directly from the complex. These are a cyclic immonium ion, formed after elimination of AgH from the Ag+-proline complex, another cyclic immonium ion formed after the elimination of both AgH and CO2, and finally an ion formed as the product of a reductive-elimination reaction in which H2 is lost as a neutral. Selective and nonselective deuterium labeling experiments and hybrid density functional calculations have been employed to probe fragmentation mechanisms that account for all experimental results. The mechanisms for the competitive losses of AgH and H2 from the Ag+-proline complex have been calculated at B3LYP/DZVP.

We have studied the silver ion affinities of several RCN ligands using density functional theory. It was found that they correlate linearly with experimental proton affinities, a contradiction to the HSAB principle as H + is a ‘hard’ acid, and Ag + is a ‘soft’ acid. This linear correlation between the Ag + and proton affinities diminishes as the number of RCN ligands attached to the Ag + ion increases from one to three. In the third addition step, the silver ion affinities nearly level off in agreement with the expectation that the electron donating or withdrawing properties of the R group become much less important than in the previous two steps, where the positive charge on the metal ion is not well delocalized. Delocalization of the charge of a metal ion occurs only when a sufficiently large number of ligands are attached to the metal ion. When this condition is satisfied, our data suggests that the HSAB principle may be applicable.

Proton migration in protonated glycylglycylglycine (GGG) has been investigated by using density functional theory at the B3LYP/6-31++G(d,p) level of theory. On the protonated GGG energy hypersurface 19 critical points have been characterized, 11 as minima and 8 as first-order saddle points. Transition state structures for interconversion between eight of these minima are reported, starting from a structure in which there is protonation at the amino nitrogen of the N-terminal glycyl residue following the migration of the proton until there is fragmentation into protonated 2-aminomethyl-5-oxazolone (the b(2) ion) and glycine. Individual free energy barriers are small, ranging from 4.3 to 18.1 kcal mol(-)(1). The most favorable site of protonation on GGG is the carbonyl oxygen of the N-terminal residue. This isomer is stabilized by a hydrogen bond of the type O-H.N with the N-terminal nitrogen atom, resulting in a compact five-membered ring. Another oxygen-protonated isomer with hydrogen bonding of the type O-H.O, resulting in a seven-membered ring, is only 0.1 kcal mol(-)(1) higher in free energy. Protonation on the N-terminal nitrogen atom produces an isomer that is about 1 kcal mol(-)(1) higher in free energy than isomers resulting from protonation on the carbonyl oxygen of the N-terminal residue. The calculated energy barrier to generate the b(2) ion from protonated GGG is 32.5 kcal mol(-)(1) via TS(6--7). The calculated basicity and proton affinity of GGG from our results are 216.3 and 223.8 kcal mol(-)(1), respectively. These values are 3-4 kcal mol(-)(1) lower than those from previous calculations and are in excellent agreement with recently revised experimental values.

Tandem mass spectrometry performed on a pool of 18 oligopeptides shows that the product ion spectra of argentinated peptides, the [b n + OH + Ag]+ ions and the [y n − H + Ag]+ ions bearing identical sequences are virtually identical. These observations suggest strongly that these ions have identical structures in the gas phase. The structures of argentinated glycine, glycylglycine, and glycylglycylglycine were calculated using density functional theory (DFT) at the B3LYP/DZVP level of theory; they were independently confirmed using HF/ LANL2DZ. For argentinated glycylglycylglycine, the most stable structure is one in which Ag+ is tetracoordinate and attached to the amino nitrogen and the three carbonyl oxygen atoms. Mechanisms are proposed for the fragmentation of this structure to the [b2 + OH + Ag]+ and the [y2 − H + Ag]+ ions that are consistent with all experimental observations and known calculated structures and energetics. The structures of the [b2 − H + Ag]+ and the [a2 − H + Ag]+ ions of glycylglycylglycine were also calculated using DFT. These results confirm earlier suggestions that the [b2 − H + Ag]+ ion is an argentinated oxazolone and the [a2 − H + Ag]+ an argentinated immonium ion.

Density functional calculations at B3LYP/DZVP were used to obtain structural information, relative free energies of different isomers and binding energies for the following reaction in the gas phase: M+ + (glycyl)nglycine → M–(glycyl)nglycine+, where M = Ag or Cu and n = 0–2. For the complexes with Cu+, optimizations were also performed at B3LYP/6–31++G(d,p) and single-point calculations at MP2(fc)/6–311++G(2df,2p)//B3LYP/DZVP. The calculated binding energies for the Cu+ complexes are all higher than those of the structurally similar Ag+ ions. These calculated binding energy differences become larger as the size of the ligand increases. For all the Cu+ complexes examined, the coordination number of the copper ion does not exceed two, whereas for the silver complexes tri- and tetracoordinate Ag+ structures are calculated to be at low energy minima. Significant structural and relative free energy differences occur between the lowest energy ‘zwitterionic ’ forms of the M–(glycyl)nglycine+ complexes.

The [M − nH + mNa](m−n)+ and [M − nH + mK](m−n)+ ions are common in the electrospray mass spectra of proteins and peptides. The feasibility of forming these ions in the gas phase via collision activation and/or ion-molecule reaction is investigated. Sodium and potassium affinities of the N-methylacetamide anion, the acetate anion, and the 1-propanamide anion have been calculated using density functional theory at the B3LYP/6-311+ +G(d,p) level of theory. These anions were chosen as models for the functional groups on a protein or peptide. These affinity values are then used to calculate reaction enthalpies of alkali hydroxides, chlorides, and hydrates with N-methylacetamide, acetic acid, the acetate anion, and 1-propanamine, model reactions that may lead to formation of the [M − nH + mNa](m−n)+ and [M − nH + mK](m−n)+ ions. It is found that a number of these reactions are exothermic or slightly endothermic (ΔH 0 < + 20 kcal/mol) and are accessible after collision activation in the lens region. The potential energy hypersurfaces of model reactions between NaOH and formamide as well as NaCl and formamide show relatively flat surfaces devoid of significant barriers.

Density functional calculations at B3LYP/6-31+G(d) and B3LYP/DZVP are reported for Mg(NH 3 ) n +· , where n = 1–6 and for some solvated ions Mg(NH 3 ) n +· … NH 3 ( n = 1–3, 6). After correction for basis set superposition errors, the enthalpies for sequential addition of NH 3 to Mg +· resulting from direct coordination to the metal are 38.1, 26.6, 21.2, 13.7, 12.1, and 11.3 kcal mol −1 . The free energies for these same addition reactions are all negative, although for complexes with n ≥ 4 the values are very small. Attempts at optimising structures with higher coordination numbers all resulted in the formation of solvated octahedral complexes. Enthalpies for solvation through hydrogen bonding to one of the ligated NH 3 molecules are all less than 16 kcal mol −1 and decrease rapidly as the number of ligated NH 3 molecules increases. Molecular orbital calculations at B3LYP/DZVP have been used to optimise structures for ions Ag(NH 3 ) n + , where n = 1–6. The five-coordinate and six-coordinate structures have very small binding enthalpies (4.3 and 2.6 kcal mol −1 ) and the free energies for formation of these ions are positive. The binding energies for the addition of the first and second NH 3 molecules added to Ag + are 40.1 and 36.1 kcal mol −1 , while those for the third and fourth additions are much smaller (15.1 and 11.0 kcal mol −1 ). Adducts up to n = 3 have been detected in electrospray experiments. The first three adducts of Ag + with NH 3 have been formed in the selected ion flow tube apparatus and multicollision induced dissociation experiments show Ag(NH 3 ) 3 + to have a lower binding enthalpy than both Ag(NH 3 ) 2 + and Ag(NH 3 ) + .

Molecular orbital calculations at B3LYP/6-31++G(d,p) are reported for bases 2-(aminomethyl)-5-oxazolone, 2-(aminomethyl)-4-methyl-5-oxazolone, 2-phenyl-5-oxazolone, and 2-phenyl-4 methyl-5-oxazolone and for the cations formed by protonation of these bases on their imino nitrogens. Structures and relative energies for isomers generated by protonation at each of the four heteroatoms of 2-(aminomethyl)-5-oxazolone are reported. Lithium and silver cations both add to 2-(aminomethyl)-5-oxazolone, but unlike the proton, they bind with two heteroatoms simultaneously. For both the lithiated and argentinated 2-(aminomethyl)-5-oxazolone cations the lowest energy isomers have the metal coordinated with the two nitrogen atoms. Proton affinities of these bases are in the range 217.0-221 kcal mol -1 , with the methyl group at C4 increasing the proton affinity by 3 kcal mol -1 . Single-point calculations were performed at MP4(fc)/6-311++G(2df,p)//B3LYP/6-31++G(d,p) for 2-(aminomethyl)-5-oxazolone, diketopiperazine, glycine, and alanine and their conjugate acids. The proton affinities from this level of theory are lower by as much as 2.7 kcal mol -1 than those calculated at B3LYP/6-31++G(d,p). Enthalpies of formation calculated at B3LYP/6-31++G(d,p) from isodesmic reactions for glycine, alanine, and their conjugate acids are all within 1 kcal mol -1 of the experimental values, but those calculated at MP4 deviate by as much as 4.8 kcal mol -1 . Enthalpies of formation from atomization reactions at the MP4 level are in larger disagreement with experimental values.

The presence of an interacting water or methanol molecule has been shown to catalyze the 1,3-proton shift in a peptide linkage between the tautomers of protonated formamide and glycylglycylglycine. Density functional theory calculations at the B3LYP/6-31++G(d,p) level of theory show that, for glycylglycylglycine, the forward barrier of this shift decreases from a free energy at 298 K of 39.6 kcal/mol in the absence of solvent to 26.7 kcal/mol in the presence of water and to 22.0 kcal/mol in the presence of methanol. Protonation at the amide nitrogen of the second residue results in a large increase in the C -N bond distance from 1.336 to 1.519 A, whereas protonation at the carbonyl oxygen leads to a decrease in the C-N bond distance from 1.336 to 1.321 A. Solvent-catalyzed tautomerism may play an important role in the fragmentation of electrosprayed, protonated peptides in the gas phase.

The complexation of the Pt-based anti-cancer drug oxaliplatin (OxPt) with biological ligands other than DNA is believed to be a major cellular sink for the drug reducing its therapeutic effect and acting as a potential cause of toxicity. In this paper, linear ion trap electrospray ionization mass spectrometry was employed to study the interaction of oxaliplatin with the cytoplasmic thiol containing tripeptide ligand γ-l-glutamyl-l-cysteinyl-glycine (GSH) this being the most abundant low-molecular-weight thiol containing molecule in human cells. Evidence of protonated dimers and multimers of oxaliplatin, protonated multimers of glutathione as well as several different combinations of these protonated species is presented. Most species observed were unambiguously assigned and compared to their theoretical isotopic patterns. Fragmentation of the collisionally-activated protonated complex of glutathione with oxaliplatin [GSH + OxPt + H](+) resulted in the formation of several species. No experimental evidence for [GSH + H](+) formation from the [OxPt + GSH + H](+) precursor was observed. Density functional calculations at B3LYP/LANL2DZ were used to obtain structural information and relative free energies of different isomers of the observed precursor [OxPt + GSH + H](+) both in the gas phase and in solution as well as to probe its fragmentation, highlighting mechanisms that account for all the experimental results. Data are presented to show several binding modes between electron rich sites such as S, N, O centers of GSH and the Pt metal of oxaliplatin. Calculations were also employed to obtain proton affinities and free energies of key reactions. The proton affinities of GSH and OxPt at 298 K were calculated to be 255.3 and 233.5 kcal mol(-1) respectively. The enthalpy and free energy, based on the most thermodynamically favored conformers of the reactants and products, for the addition reaction [Pt(dach)](2+) + [GSH - H](-) → [GSH - H + Pt(dach)](+) (where dach represents diaminocyclohexane) in the gas phase at 298 K were determined to be -311.3 and -290.2 kcal mol(-1) respectively. Similarly, the enthalpy of the gas phase reaction [Pt(dach)](2+) + GSH → [GSH + Pt(dach)](2+) at 298 K was determined to be -169.2 kcal mol(-1).

This paper describes a set of fast and selective high performance liquid chromatography (HPLC) methods coupled to electro-spray ionisation linear ion trap mass spectrometry (ESI-MS), sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) and UV detection for in vitro studies of the bifunctional adducts of oxaliplatin with mono-nucleotides, di-nucleotides and cellular DNA. The stationary phases and the optimised conditions used for each separation are discussed. Interaction of oxaliplatin with A and G mono-nucleotides resulted in the formation of five bifunctional platinum diaminocyclohexane (DACHPt) adducts. These were two isomers of the A-DACHPt-A and A-DACHPt-G adducts, and one G-DACHPt-G adduct, as confirmed by MS/MS spectra obtained by collision induced dissociation. These adducts were also characterised by UV absorption data and SF-ICP-MS elemental (195)Pt and (31)P signals. Further, interaction of oxaliplatin with AG and GG di-nucleotides resulted in the formation of three adducts: DACHPt-GG and two isomers of the DACHPt-AG adduct, as confirmed by ESI-MS and the complementary data obtained by UV and SF-ICP-MS. Finally, a very sensitive LC-ICP-MS method for the quantification of oxaliplatin GG intra-strand adducts (DACHPt-GG) was developed and used for monitoring the in vitro formation and repair of these adducts in human colorectal cancer cells. The method detection limit was 0.14 ppb Pt which was equivalent to 0.22 Pt adduct per 10(6) nucleotides based on a 10 μg DNA sample. This detection limit makes this method suitable for in vivo assessment of DACHPt-GG adducts in patients undergoing oxaliplatin chemotherapy.

The complexation of the Pt-based anti-cancer drug oxaliplatin (OxPt) with biological ligands other than DNA is believed to be a major cellular sink for the drug reducing its therapeutic potential and acting as a potential cause of toxicity. In this paper, the very first hypothesis driven investigation of the role of the naturally abundant cytoplasmic dipeptide ligand β-alanyl-l-histidine dipeptide (carnosine) in OxPt detoxification is presented. In vitro studies on hepatocellular carcinoma HepG2 cells suggest that carnosine may inhibit the cytotoxic action of OxPt most likely through the formation of complexes that are less cytotoxic than OxPt alone. Evidence is provided to suggest that pre-exposure of HepG2 cells to elevated levels of carnosine appears to have a lasting effect on reducing the cytotoxicity of OxPt even after the removal of the externally added carnosine. This effect, however, is likely under kinetic control as its magnitude was shown not to vary significantly with the level of carnosine exposure within the concentration range used in this study. Various mass spectrometry techniques employing electrospray ionization and chip nanospray were employed to study the interaction of oxaliplatin with carnosine as well as two of its derivatives β-alanyl-N-methylhistidine (anserine) and N-acetylcarnosine (NAC). Evidence of complexation between OxPt and each of the three ligands examined is presented. Most species observed were unambiguously assigned and compared to their theoretical isotopic patterns. Common fragmentation products due to the collisionally-activated protonated complexes of each of the ligands examined with OxPt, [M + OxPt + H](+), where M = carnosine, anserine or NAC, were reported. Density functional calculations at the B3LYP/LANL2DZ level were used to obtain structural information and relative free energies of different isomers of the observed precursor [Carnosine + OxPt + H](+) both in the gas phase and in solution as well as to probe its fragmentation, highlighting plausible fragmentation mechanisms that account for all the experimental results. Data are presented to show several binding modes between electron rich sites such as N and O centers of carnosine and the Pt metal of OxPt. Calculations were also employed to obtain proton affinities and free energies of key reactions. The proton affinities of carnosine, anserine and NAC at 298 K were calculated to be 254.4, 255.9 and 250.2 kcal mol(-1) respectively. To the best of our knowledge the proton affinities of anserine and N-acetyl-carnosine are the first reported values in the literature.