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Isothermal titration calorimetry, circular dichroism (CD) techniques, and

Bioaccumulation potential is critical in PBT and risk assessment of chemicals. However, for ionic liquids (ILs), this aspect remains neglected. It is especially important to fill this gap, because for this group of compounds, existing data confirm their risk of being environmentally persistent and toxicity. Moreover, considering preliminary reports on the interactions of ILs with lipids, it may be assumed that ILs have a higher potential for bioaccumulation than indicated by previous estimations built upon octanol–water partition coefficients. Moreover, the bioconcentration of ionizable chemical compounds may also be strongly related to plasma protein contents. Therefore, in this work, the affinity of a set of imidazolium cations and organic anions, and their combination to human serum albumin (HSA) was determined. The obtained results reveal that both cations and anions can be strongly bound to HSA, and blood proteins might play an important role in overall bioaccumulation. Furthermore, it was observed that HSA binding properties towards IL cations depend on the hydrophobicity of cations. The obtained data also provide indication that cation–anion interaction may affect ILs ions affinity to HSA.

This work reports detailed characteristics of the antimicrobial peptide Intestinalin (P30), which is derived from the LysC enzyme of Clostridium intestinale strain URNW. The peptide shows a broader antibacterial spectrum than the parental enzyme, showing potent antimicrobial activity against clinical strains of Gram-positive staphylococci and Gram-negative pathogens and causing between 3.04 ± 0.12 log kill for Pseudomonas aeruginosa PAO1 and 7.10 ± 0.05 log kill for multidrug-resistant Acinetobacter baumannii KPD 581 at a 5 μM concentration. Moreover, Intestinalin (P30) prevents biofilm formation and destroys 24-h and 72-h biofilms formed by Acinetobacter baumannii CRAB KPD 205 (reduction levels of 4.28 and 2.62 log CFU/mL, respectively). The activity of Intestinalin is combined with both no cytotoxicity and little hemolytic effect against mammalian cells. The nuclear magnetic resonance and molecular dynamics (MD) data show a high tendency of Intestinalin to interact with the bacterial phospholipid cell membrane. Although positively charged, Intestinalin resides in the membrane and aggregates into small oligomers. Negatively charged phospholipids stabilize peptide oligomers to form water- and ion-permeable pores, disrupting the integrity of bacterial cell membranes. Experimental data showed that Intestinalin interacts with negatively charged lipoteichoic acid (log

The potentiometric titration (PT) method has been applied for the first time to investigate the stability of L-ascorbic acid (H2Asc) and to determine its degradation products in aqueous solutions. The presented electrochemical procedures can be considered to be a fast, simple and inexpensive way to control the stability of H2Asc in a regular analytical practice as well as in the chemical and pharmaceutical industries. Experimental data as well as modeling suggest that the enolic form of 2,3-diketogulonic acid predominates in a solution as the main product of dehydroascorbate (DHA) degradation. Furthermore, the PT results supported by conductometric measurements (CM) and electrospray ionization mass spectrometry (ESI/MS) data enable us to propose the putative mechanism of the H2Asc decomposition. Moreover, it has been proven that among different types of investigated electrolytes (KNO3, KClO4 and KSCN), the thiocyanate ions (SCN-) reveal the stabilizing effect against the degradation of H2Asc. Thus, the presence of SCN- in the H2Asc solution is proposed as an alternative way for some organic solvents earlier used. Finally, a new paraffin-protection-layer procedure has been recommended for studying as well as storage of the solutions comprising components sensitive to external factors (e.g. O2, CO2) and to evaporation.

In this paper, we describe the chemical synthesis, preliminary evaluation of antimicrobial properties and mechanisms of action of a novel group of lipidated derivatives of three naturally occurring α-helical antimicrobial peptides, LL-I (VNWKKVLGKIIKVAK-NH2), LK6 (IKKILSKILLKKL-NH2), ATRA-1 (KRFKKFFKKLK-NH2). The obtained results showed that biological properties of the final compounds were defined both by the length of the fatty acid and by the structural and physico-chemical properties of the initial peptide. We consider C8–C12 length of the hydrocarbon chain as the optimal for antimicrobial activity improvement. However, the most active analogues exerted relatively high cytotoxicity toward keratinocytes, with the exception of the ATRA-1 derivatives, which had a higher selectivity for microbial cells. The ATRA-1 derivatives had relatively low cytotoxicity against healthy human keratinocytes but high cytotoxicity against human breast cancer cells. Taking into account that ATRA-1 analogues carry the highest positive net charge, it can be assumed that this feature contributes to cell selectivity. As expected, the studied lipopeptides showed a strong tendency to self-assembly into fibrils and/or elongated and spherical micelles, with the least cytotoxic ATRA-1 derivatives forming apparently smaller assemblies. The results of the study also confirmed that the bacterial cell membrane is the target for the studied compounds.

Efficient radiotherapy requires the concomitant use of ionizing radiation (IR) and a radiosensitizer. In the present work uracil-5-yl O-sulfamate (SU) is tested against its radiosensitizing potenti...

This study investigates short cationic antimicrobial lipopeptides composed of 2–4 amino acid residues and C12-C18 fatty acids attached to the N-terminal part of the peptides. The findings were discussed in the context of the relationship among biological activity, self-assembly, stability, and membrane interactions. All the lipopeptides showed the ability to self-assemble in PBS solution. In most cases, the critical aggregation concentration (CAC) much surpassed the minimal inhibitory concentration (MIC) values, suggesting that monomers are the main active form of lipopeptides. The introduction of β-alanine into the peptide sequence resulted in a compound with a high propensity to fibrillate, which increased the peptide stability and activity against S. epidermidis and C. albicans and reduced the cytotoxicity against human keratinocytes. The results of our study indicated that the target of action of lipopeptides is the bacterial membrane. Interestingly, the type of peptide counterion may affect the degree of penetration of the lipid bilayer. In addition, the binding of the lipopeptide to the membrane of Gram-negative bacteria may lead to the release of calcium ions necessary for stabilization of the lipopolysaccharide layer.

Background: Antibacterial peptidyl derivative - Cystapep 1, was previously found to be active both against antibiotic-resistant staphylococci and streptococci as well as antibioticsusceptible strains of these species. Therefore, it is a promising lead compound to search for new antimicrobial peptidomimetics. Objective: We focused on identifying structural elements that are responsible for the biological activity of Cystapep 1 and its five analogues. We tried to find an answer to the question about the mechanism of action of the tested compounds. Therefore, we have investigated in details the possibility of interacting these compounds with biological membrane mimetics. Methods: The subject compounds were synthesized in solution, purified and characterized by HPLC and mass spectrometry. Then, the staphylococci susceptibility tests were performed and their cytotoxicity was established. The results of Cystapep 1 and its analogues interactions with model target were examined using the DSC and ITC techniques. At the end the spatial structures of the tested peptidomimetics using NMR technique were obtained. Results: Antimicrobial and cytotoxicity tests show that Cystapep 1 and its peptidomimetic V are good drug candidates. DSC and ITC studies indicate that disruption of membrane is not the only possible mechanism of action of Cystapep 1-like compounds. For Cystapep 1 itself, a multi-step mechanism of interaction with a negatively charged membrane is observed, which indicates other processes occurring alongside the binding process. The conformational analysis indicated the presence of a hydrophobic cluster, composed of certain side chains, only in the structures of active peptidomimetics. This can facilitate the anchoring of the peptidyl derivatives to the bacterial membrane. Conclusion: An increase in hydrophobicity of the peptidomimetics improved the antimicrobial activity against S. aureus, however there is no simple correlation between the biological activity and the strength of interactions of the peptidyl with bacterial membrane.

Differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC) techniques have been used to describe physicochemical properties of polypeptide LL-37. LL-37 is a 37-residue, amphipathic, helical peptide, the only cathelicidin-derived antimicrobial peptide found in the human organism. Thermal stability of the LL-37 peptide in a water solution was measured by DSC over the 288.15–333.15 K range. Furthermore, the ITC method supported by theoretical calculations (peptide–ligand docking) were used to study the interactions between LL-37 and some divalent metal ions, namely Cu2+, Zn2+, and Ni2+ ions as well as acetylsalicylic acid, ascorbic acid, and caffeine molecules. It has been proven that under experimental conditions, the LL-37 peptide reveals affinity only toward Cu2+ and Zn2+ ions. The stoichiometry, conditional binding constants, logKITC, and thermodynamic parameters (∆ITCG, ∆ITCH, T∆ITCS) of the resulting Cu(II) and Zn(II) complexes were determined and discussed.

Isothermal titration calorimetry (ITC) and potentiometric titration (PT) methods were used to study the interactions of copper(II) ions with GAG, GDG, GKG, and GHG peptides. The calorimetric measurements were run in a MES buffer with the pH value of 6.0 at 298.15 K. Based on the results of PT data supported by theoretical calculations, the dissociation constants were calculated for the investigated peptides. The quantification of the proton competition with the metal for the peptide and incorporation it into the ITC data analysis enabled to obtain the pH-independent parameters, namely the binding constants (K) and the free energy of binding (ΔG). Furthermore, the relationship between the proposed coordination modes of the considered peptides and the thermodynamic parameters (K, ΔG and ΔH) has been discussed.

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung's disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung's disease) from 264 hospitals (89 in high-income countries, 166 in middle-income countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p

Efficient radiotherapy requires the concomitant use of ionizing radiation (IR) and a radiosensitizer. In the present work uracil-5-yl O-sulfamate (SU) is tested against its radiosensitizing potential. The compound possesses appropriate dissociative electron attachment (DEA) characteristics calculated at the M06-2X/6-31++G(d,p) level. Crossed electron–molecular beam experiments in the gas phase demonstrate that SU undergoes efficient DEA processes, and the single C–O or S–O bond dissociations account for the majority of fragments induced by electron attachment. Most DEAs proceed already for electrons with kinetic energies of ∼0 eV, which is supported by the exothermic thresholds calculated at the M06-2X/aug-cc-pVTZ level. However, in water solution under reductive conditions and physiological pH, SU does not undergo radiolysis, which demonstrates the crucial influence of aqueous environment on the radiosensitizing properties of modified nucleosides.

It is widely believed that the hydrophobic effect governs the binding of guest molecules to cyclodextrins (CDs). However, it is also known that high hydrophobicity of guest molecules does not always translate to the formation of stable inclusion complexes with CDs. Indeed, a plethora of other factors can play a role in the efficiency of guest–CD interactions, rendering structure-based prediction of the complexation efficiency with CDs a non trivial task. In this combined experimental and computational study, we examine the major structural factors governing complexation efficiency of polycyclic aromatic drug-like compounds with natural CDs, using as an example iminostilbene and its N-substituted derivatives. We find that purely hydrophobic IS derivatives show negligible complexation efficiency with CDs and only IS with hydrophilic substituents form stable inclusion complexes in water. We show that the balance between the guest solubility and its affinity to CDs is critical for the effective formation of inclusion complexes. Finally, our results demonstrate that guest–host hydrogen bonds facilitate the formation of crystalline inclusion complexes with CDs.

Background Infantile hemangioma (IH) is the most common vascular tumor of childhood and infancy. It is distinguished by rapid proliferation of endothelial cells during the first year of life followed by spontaneous regression thereafter. One of the possible factors responsible for the IH development is vascular endothelial grow factor (VEGF). The purpose of this study was to evaluate the influence of selected polymorphisms in the genes coding for VEGF-A (+405 G/C, rs2010963; +936 C/T, rs3025039) and its receptor VEGFR-2 (+1416 T/A, rs1870377; -271 G/A, rs7667298) on the susceptibility to infantile hemangioma. Methods We performed a case-control study of 99 Polish children hospitalized due to IH and compared them with matched healthy control subjects. The polymorphisms were ascertained through genotyping by PCR-RFLP assay, PCR-HRM, or the allelic discrimination method. Results The study revealed a lower odds of infantile hemangioma in individuals with GG genotype or G allele for +405 G/C VEGF-A polymorphism (ORdis = 0.52, P = 0.023 and ORdis = 0.63, P = 0.025, respectively). No association was observed for the remaining VEGF and VEGFR-2 polymorphisms and IH risk. Conclusions In our study, none of the investigated VEGF-A and VEGFR-2 genes polymorphisms was found to be an independent prognostic marker for infantile hemangioma. However, there is evidence that individuals carrying at least one G allele of +405 G/C VEGF-A polymorphism have significantly lower risk of IH.

C60 fullerene is reported to directly interact with biomolecules, such as aromatic mutagens or anticancer drugs. Therefore, it is extensively studied for its potential application in the fields of drug delivery and chemoprevention. Understanding the nature of fullerene-drugs interactions might contribute to optimization and modification of the existing chemotherapy systems. Possible interactions between ICR-191, a model acridine mutagen, with well-established biophysical properties and mutagenic activity, and C60 fullerene aqueous solution were investigated by broad range of biophysical methods, such as Dynamic Light Scattering, Isothermal Titration Calorimetry, and Atomic Force Microscopy. Additionally, to determine biological activity of ICR-191-C60 fullerene mixtures, Ames mutagenicity test was employed. It was demonstrated that C60 fullerene interacts non-covalently with ICR-191 and has strong affinity to bacterial membranes. The obtained results provide practical insight into C60 fullerene interactions with aromatic compounds.

Histaminol [4(5)-(B-hydroxyethyl)imidazole, 4-(1H-imidazol-2-yl)ethanol, L] is an analogue of histamine and its minor metabolite. So far its properties have not been studied in detail due to the synthetic difficulties. Here, the structure and acid-base properties of histaminol, as well as the results of studies on its copper(II) complexes in solid state and aqueous solution are reported. Stability constants of the histaminol–CuII sys- 11 tem are measured and each stage of the complex formation is illustrated with the relevant crystal structure and the EPR spectrum.

Isothermal titration calorimetry, potentiometric titration and circular dichroism spectroscopy were used to study the interaction of copper(II) ions with Argireline (Ac-Glu-Glu-Met-Gln-Arg-Arg-NH2) and three of its point mutation derivatives: Glu-Ala-Met-Gln-Arg-Arg-NH2 (AN1), Glu-Ala-His-Gln-Arg-Arg-NH2 (AN2) and Glu-Ala-Met-Gln-Ala-Arg-NH2 (AN3). Under the experimental conditions (20 mmol·L−1 Caco solution, pH 6, 298.15 K), copper(II) ions form 1:1 complexes with the peptides Argireline, AN1, and AN2. The complexation reactions are entropy-driven processes. The stability of the resulting complexes increases in the order log10KCu(AN1)

Understanding the metal ion-protein interactions is crucial in transport, accumulation, and excretion of metals. Furthermore, it seems to be highly important to investigate the role of such complexes in many diseases, such as cancer and neurodegenerative disorders. Unexpectedly, such studies in the systems comprising peptides and Ni2+ ions are still scarce and should be given more importance – particularly considering the toxicity and carcinogenicity of nickel compounds on the living organisms. We report herein the results of a study on the interactions of Ni2+ ions and four pentapeptide analogs: EYHHQ (p1), EHYHQ (p2), HEYHQ (p3), and HEYQH (p4). Potentiometric titration was used to study acid-base properties as well as binding properties of the investigated peptides. Furthermore, stoichiometry of the peptide complexes with Ni2+ ions was evaluated by steady-state fluorescence spectroscopy and potentiometric titration method. Additionally, based on the density functional theory (DFT) calculations, we propose the most likely structures of the complexes of the peptides p1-p4 with Ni2+ ions. It was found that all the peptides form 1:1 and 1:2 thermodynamically stable complexes with Ni2+ cation. In particular, we observed that the interaction between the metal ion and histidine-containing peptide sequences does not depend only on histidines splicing, but also on their orientation in respect to other amino acids in the sequence. Also, the closer proximity of His residue in these short peptides does not increase complex stability, due to stacking interaction between the neighboring imidazole rings.

To rigorously characterize the interactions of sodium dodecyl sulfate (SDS) with bovine serum albumin (BSA) a set of experimental methods, namely isothermal titration calorimetry, conductometric titration, steady-state fluorescence spectroscopy, differential scanning calorimetry and circular dichroism spectroscopy, supported by in silico analysis have been applied. The influence of pH and temperature on the binding mode has been revealed. At a low molar ratio of SDS to BSA up to ca. 16:1, there are at least two structurally distinct binding sites in BSA. The formation of SDS-BSA complexes is an enthalpy-driven process in which the van der Waals interactions play a crucial role. The first binding site, located close to the Trp-134 residue within the sub-domain IA, is pH-independent and binds two molecules of SDS per one molecule of BSA whereas the total number of SDS molecules bound to the second site of albumin is affected by temperature and pH. The saturation of the first binding site of BSA (ca. 0.009 mg of SDS per 1 mg of BSA) is sufficient to thermally stabilize the helical conformation of BSA. The presented results have important structural and thermodynamic implications to understand the influence of a widely used anionic surfactant on globular protein functionality in modern branches of chemistry.

We present a review of the available literature concerning pKa values and methods for the determination of selected anticancer drugs as well as the most up-to-date knowledge on their different ionic forms depending on solution pH. Additionally, to clarify the existing state of knowledge we have presented an overview on the obtained pKa values with the use of experimental and computational methods. As a result, we have demonstrated and proposed acid-base equilibria of cyclophosphamide (CF), ifosfamide (IF), 5-fluorouracil (5-FU), methotrexate (MTX), and imatinib (IMT) in an aqueous solution, and their species distribution curves as a function of pH calculated on the basis of the acid dissociation constants, which are as follows: CF pKa1 2.3, pKa2 11.1 [CF-H2L+/CF-HL/CF-L−] IF pKa1 5-FU pKa1 7.5, pKa2 9.0 [5-FU-H2L/5-FU-HL−/5-FU-L2−] MTX pKa1 2.9, pKa2 4.6, pKa3 6.6 [MTX-H3L+/MTX-H2L/MTX-HL−/MTX-L2−] IMT pKa1 2.5, pKa2 4.0, pKa3 8.3 [IMT-H3L3+/IMT-H2L2+/IMT-HL+/MTX-L].

The alarming raise of multi-drug resistance among human microbial pathogens makes the development of novel therapeutics a priority task. In contrast to conventional antibiotics, antimicrobial peptides (AMPs), besides evoking a broad spectrum of activity against microorganisms, could offer additional benefits, such as the ability to neutralize toxins, modulate inflammatory response, eradicate bacterial and fungal biofilms or prevent their development. The latter properties are of special interest, as most antibiotics available on the market have limited ability to diffuse through rigid structures of biofilms. Lipidation of AMPs is considered as an effective approach for enhancement of their antimicrobial potential and in vivo stability, however, it could also have undesired impact on selectivity, solubility or the aggregation state of the modified peptides. In the present work, we describe the results of structural modifications of compounds designed based on cationic antimicrobial peptides DK5 and CAR-PEG-DK5, derivatized at their N-terminal part with fatty acids with different lengths of carbon chain. The proposed modifications substantially improved antimicrobial properties of the final compounds and their effectiveness in inhibition of biofilm development as well as eradication of pre-formed 24 h old biofilms of Candida albicans and Staphylococcus aureus. The most active compounds (C5-DK5, C12-DK5 and C12-CAR-PEG-DK5) were also potent against multi-drug resistant Staphylococcus aureus USA300 strain and clinical isolates of Pseudomonas aeruginosa. Both experimental and in silico methods revealed strong correlation between the length of fatty acid attached to the peptides and their final membranolytic properties, tendency to self-assemble and cytotoxicity.

Antimicrobial resistance is a major healthcare threat globally. Xanthines, including caffeine and pentoxifylline, are attractive candidates for drug repurposing, given their well-established safety and pharmacological profiles. This study aimed to analyze potential interactions between xanthines and aromatic antibiotics (i.e., tetracycline and ciprofloxacin), and their impact on antibacterial activity. UV-vis spectroscopy, statistical-thermodynamical modeling, and isothermal titration calorimetry were used to quantitatively evaluate xanthine-antibiotic interactions. The antibacterial profiles of xanthines and xanthine-antibiotic mixtures towards important human pathogens Staphylococcus aureus, Enterococcus faecium, Escherichia coli, Acinetobacter baumannii, Klebsiella pneumoniae, and Enterobacter cloacae were examined. Caffeine and pentoxifylline directly interact with ciprofloxacin and tetracycline, with neighborhood association constant values of 15.8–45.6 M− 1 and enthalpy change values up to -4 kJ M− 1. Caffeine showed antibacterial activity (minimum inhibitory concentration, 4–8 mg/mL) toward Gram-negative bacteria. Caffeine enhanced the antibacterial activity of the tested antibiotics in most pathogens tested. Antagonistic effects of caffeine were observed only with ciprofloxacin toward Gram-positive pathogens. Xanthines interact with aromatic antibiotics at the molecular and in vitro antibacterial activity level. Given considerable exposure to caffeine and pentoxifylline, these interactions are relevant for the effectiveness of antibacterial pharmacotherapy, and may help to identify optimal treatment regimens in the era of multidrug resistance.

The kinetics and thermodynamics have been studied for the reactions of the copper(II) complexes with iminodiacetate (ida), 2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen) as ligands. The kinetics of substitution reactions of two aqua ligands for bipy and phen in the [Cu(ida)(H2O)2] coordination compound has been studied in water and three type of aqueous solutions of the following surfactants: anionic sodium dodecyl sulfate (SDS), cationic hexadecyl trimethyl-ammonium bromide (CTAB) and nonionic t-octylphenoxypolyetoxyethanol (Triton X-100). The progress of the substitution reactions in the studied solutions was monitored spectrophotometrically using the stopped-flow method. The studies have allowed the determination of the effect of the type of surfactant solutions on the rate of the substitution reaction. Moreover, the order of studied reactions has been determined. The research performed has also allowed us to propose the reaction mechanism of the [Cu(ida)(H2O)2] binary complex with chelate ligands (bipy or phen). In addition, the thermodynamic stability of complexes under study in aqueous solutions has been examined using the potentiometric titration method. Moreover, the potential scavenging activity of the copper(II) complexes has been investigated towards the superoxide radical.

The crystal and molecular structures of a new dinuclear oxidovanadium(IV) complex with the N-(phosphonomethyl)iminodiacetate (pmida) ligand and the 4-amino-2-methylquinolinium ([amqH]+) cation of the molecular formula [amqH]4[V2O2(pmida)2]6H2O have been determined. The phosphonate groups in the two pmida4− ligands form two bridges between adjacent V4+ atoms, resulting in the formation of a [V2O2(pmida)2]4− dimer with a V2O4P2 eight-membered ring. This is the first example of a quinoline derivative complex containing the [V2O2(pmida)2]4− ion. The susceptibility curve for the complex exhibits a maximum at approximately 10 K, indicating the presence of antiferromagnetic interactions transmitted in the crystal lattice. Furthermore, the biological properties of the complex in the concentration range 1–100 μM were investigated in relation to its cytoprotective activity against oxidative damage generated exogenously using hydrogen peroxide in the hippocampal neuronal HT22 cell line (MTT tests). The obtained results were subsequently referred to the [amqH][VO(nta)(H2O)]H2O analogue as well as trolox and ascorbic acid, used as known antioxidants. It has been established that the title compound effectively protects HT22 from oxidative damage and is a potentially good candidate for further evaluation of the mechanism of its action.

New oxidovanadium(IV) complexes with a modification of the ligand in the VO 2+ coordination sphere were synthesized. [VO(mIDA)(dmbipy)]∙1.5H 2 O and [VO(IDA)(dmbipy)]∙2H 2 O were obtained as dark green crystals and grey-green powder, respectively (mIDA = N-methyliminodiacetic anion, IDA = iminodiacetic anion, dmbipy = 4,4′-dimethoxy-2,2′-dipyridyl). The crystal structure of [VO(mIDA)(dmbipy)]·1.5H 2 O has been determined by the X-ray diffraction method. The studies of structure of [VO(mIDA)(dmbipy)]∙1.5H 2 O have shown that this compound occurs in the crystal as two rotational conformers. Furthermore, the stability constants of [VO(mIDA)(dmbipy)]∙1.5H 2 O and [VO(IDA)(dmbipy)]∙2H 2 O complexes in aqueous solutions were studied by using the potentiometric titration method and, consequently, determined using the Hyperquad2008 program. Moreover, the title complexes were investigated as antioxidant substances. The impact of the structure modification in the VO 2+ complexes on the radical scavenging activity has been studied. The ability to scavenge the superoxide radical by two complexes - [VO(mIDA)(dmbipy)]·1.5H 2 O and [VO(IDA)(dmbipy)]·2H 2 O was studied by cyclic voltammetry (CV) and nitrobluetetrazolium (NBT) methods. The title complexes were also examined by the spectrophotometric method as scavengers of neutral organic radical - 1,1-diphenyl-2-picrylhydrazyl (DPPH ∙ ) and radical cation - 2,2'-azinobis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS ∙+ ). Furthermore, the biological properties of two oxidovanadium(IV) complexes were investigated in relation to its cytoprotective properties by the MTT and LDH tests based on the hippocampal HT22 neuronal cell line during the oxidative damage induced by hydrogen peroxide. Finally, the results presented in this paper have shown that the both new oxidovanadium(IV) complexes with the 4,4′-dimethoxy-2,2′-dipyridyl ligand can be treated as the cytoprotective substances.

The crystal and molecular structure of the new copper(II) complex with nitrilotriacetate (nta) and 1,10-phenanthroline (phen) ligands of the [Cu(phen)2Cu(nta)(phen)]2[Cu(Hnta)2]·20H2O molecular formula has been determined. The compound comprises the dianionic mononuclear entity, [Cu(Hnta)2]2−, and two monocationic dinuclear units, [Cu(phen)2Cu(nta)(phen)]+, in which the Cu(II) ions are bridged by one oxygen atom of the nta ligand in the rarely found μ1,1–O bridging mode. The complex was characterized by spectroscopic (IR, FIR and EPR) methods and magnetic measurements as well as thermogravimetry (TG). The magnetic measurements revealed an antiferromagnetic coupling between the Cu(II) ions in the dinuclear unit. Based on the experimental data supported by density functional theory (DFT) calculations the correlation between the coordination mode of the Cu(II) ions and magnetic properties of the compound studied has been discussed.

Short cationic antimicrobial lipopeptides with surfactant-like structure are promising antibiotic candidates that preferentially target microbial membranes. Therefore, we focused our study on double-chain lipopeptides, (C10-16)2Dab-KKK-NH2 and (C10-16)2Dap-KKK-NH2, where Dab and Dap are 2,4-diaminobutyric and 2,3-diaminopropionic acids, respectively. We tried to answer a question how the self-assembly behaviour affects biological activities of the tested compounds. The subject compounds were synthesized by solid-phase method and screened for their antimicrobial and haemolytic activities. Cytotoxicity tests on human keratinocytes were carried out for the most promising lipopeptides. Self-assembly properties were evaluated by both experimental and theoretical methods. Interactions with membrane models were examined using the ITC and FTIR techniques. All the lipopeptides studied showed the tendency to self-assembly in solution, and this behaviour was affected by the length of the hydrocarbon chains. Acyl chain elongation supported the formation of the bilayer structure and deprived the lipopeptides of antimicrobial activity. A multi-step mechanism of interaction with a negatively charged membrane was observed for the short-chain lipopeptides, indicating other processes accompanying the binding process. Short-chain lipopeptides were able to penetrate into the liposome's interior and/or cause the rupture of the liposome, this being compatible with their high antimicrobial activity.

The impact of oxydiacetate oxidovanadium(IV) complexes on plants is currently unknown. This report demonstrates the influence of these complexes on Arabidopsis thaliana (L.) Heynh. In the presence of 10-6M vanadium(IV) complexes, plants proceeded through their entire life cycle, with the occurrence of proper morphological and cytological organisation of leaf and root tissues. The addition of 10-1M H2O2 caused root damage, leaf necrosis, and plant death at around the seventh day, due to the destruction of the root system. Pretreatment of the plants with 10-6M of vanadium(IV) compounds: VOSO4 and VO(oda), alleviated the effects of H2O2 to some extent. Plants pretreated with 10-6M vanadium(IV) complexes survived longer despite the presence of H2O2. Considering the higher rate of plant survival in the presence of VOSO4, and the relatively high photosynthetic parameters and anthocyanin contents in the cells, we conclude that this vanadium(IV) compound can have positive effects on plants that are grown under stress conditions.

Human cystatin C (hCC) is one of the amyloidogenic molecules involved in neurodegeneration processes. Fragment 85–94, with the FHDQPHLKRK sequence, is interesting from the point of view of coordination as histidine and aspartic acid residues are potential copper(II) ion donors. Our previous studies showed that two potential binding sites are possible within this peptide chain. Therefore, the coordination abilities of each of these two metal ion binding sites have been checked. We have analysed two analogues of the native peptide, where particular histidine residues were substituted with alanine – an amino acid without a coordinating side chain: Ac-H2A (with alanine in position 2) and Ac-H6A (with alanine in position 6). NMR, potentiometric titration, UV–Vis, CD, EPR and MS studies were carried out. Obtained results showed that both ligands finally form the 4 N copper(II) complexes in a basic range of pH. However, their coordination properties are slightly different. The copper(II) binding efficiency is also different in both cases. Up to pH 6–6.5, AcH2A is more effective, but the situation is quite reversed under more basic conditions. Considering the results obtained, it can be concluded that in the unmodified peptide, the N-terminal binding site seems to be more favourable than the C-terminal.

Antimicrobial peptides (AMPs) constitute a promising tool in the development of novel therapeutic agents useful in a wide range of bacterial and fungal infections. Among the modifications improving pharmacokinetic and pharmacodynamic characteristics of natural AMPs, an important role is played by lipidation. This study focuses on the newly designed and synthesized lipopeptides containing multiple Lys residues or their shorter homologues with palmitic acid (C16) attached to the side chain of a residue located in the center of the peptide sequence. The approach resulted in the development of lipopeptides representing a model of surfactants with two polar headgroups. The aim of this study is to explain how variations in the length of the peptide chain or the hydrocarbon side chain of an amino acid residue modified with C16, affect biological functions of lipopeptides, their self-assembling propensity, and their mode of action.

In the last few years propranolol has revolutionized infantile hemangioma therapy. This nonselective β bloker has been proven to be safe and effective but the molecular bases of its actions remain unclear. One of debated theories holds that propranolol may inhibit angiogenesis and induce apoptosis. To investigate this claim, this study aims to analyze the serum and tissue profiles of VEGF and VEGRR1/2 in patients treated with propranolol. Materials and methods To assess the expression if VEGF and VEGRR1/2 we used three independent methods. First we analyzed serum VEGF levels in 50 children with IH before and 3 months after the therapy using ELISA test (I.). Then we used immunohistochemistry to evaluate tissue expression of VEGF and VEGFR1/2 in IH treated (n = 27) and not treated (n = 45) with propranolol (II.). Finally we assessed mRNA of VEGF and VEGFR1/2 in the same patients as in part II (III.). Results (I) There was no distinct decrease of VEGF level in children with IH after propranolol treatment. (II) We found no significant difference in VEGFR1 and VEGFR2 expression in hemangiomas from the study and control group. The expression of VEGF was even higher than before therapy. (III) VEGF and VEGFR1 mRNA expression was significantly lower in IH tissue after propranolol treatment compared to those without treatment. VEGFR2 demonstrated no differences in expression between the two groups. Conclusions The obtained results show distinct discrepancies between in vitro and clinical studies as well as among different methods used for analyzing the same phenomenon. Only VEGF and VEGFR1 expression in mRNA studies may prove the proposed theory of antiangiogenic properties of propranolol. Other results do not confirm it and remain inconsistent with the fantastic clinical response to this medication.

The kinetics of the aquation reaction of [Ni(ODA)(H2O)3] (where ODA = oxydiacetate) promoted by [Fe(H2O)6]3+ ions were investigated. Spectrophotometry studies were carried out at temperatures within the range 293.15–313.15 K. The concentration of [Ni(ODA)(H2O)3] was 8.67 × 10–4 mol L–1 and the concentration of the [Fe(H2O)6]3+ ions was kept within the range 0.75 × 10–4–7.50 × 10–4 mol L–1. The observable reaction rate constants increased with the increase of [Fe3+] according to the rate law: kobs = k + k1K{[Fe(H2O)6]3+}. Based on the kinetic data, the activation parameters were determined for the spontaneous step of the reaction and for the step dependent on the concentration of Fe3+ ions. A mechanism for the aquation reaction has been proposed. In the first step (the reversible part of the aquation reaction) a dinuclear intermediate product is produced and in the next step the products of the reaction, ([Ni(H2O)6]2+ and [Fe(ODA)(H2O)3]+), are formed. Nevertheless, it has turned out that the spontaneous path of the aquation reaction is also possible concurrently (independent of the presence of Fe3+ ions). However, this process is too slow to be accurately measurable.

The influence of the oxydiacetate (ODA) and thiodiacetate (TDA) ligands on the physicochemical and biological properties of the oxidovanadium(IV) ternary complexes of the VO(L)(B) type, where L denotes ODA or TDA and B denotes 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen), has been investigated. The stability of the complexes in aqueous solutions, assessed based on the potentiometric titration method, increases in the following direction: VO(TDA)(bipy)

The human Pin1 WW domain catalyzes the cis-trans isomerization of the proline peptide bond. In this study, the conformation and binding of Cu(II) ions by Pin1 were investigated. It has been found that the affinity of peptide fragments of the human Pin1 WW domain for Cu(II) ions depends on its conformation. In particular, we analyzed three peptides derived from human Pin1: the nonapeptide hPin1(14-22) (with sequence Arg-Met-Ser-Arg-Ser-Ser-Gly-Arg-Val-NH2, peptide 1) the undecapeptide hPin1(13-23) (with sequence Lys-Arg-Met-Ser-Arg-Ser-Ser-Gly-Arg-Val-Tyr-NH2, peptide 2) and its derivative Ala13Ala23hPin1(13-23) (with sequence Ala-Arg-Met-Ser-Arg-Ser-Ser-Gly-Arg-Val-Ala-NH2, peptide 3) to study the role of presence in the sequence of the flanked residues at the N- and C-terminus, i.e., Lys13 and Tyr23. The presence of heat-capacity peaks found by DSC measurements for the systems studied strongly suggests that the conformational equilibria of the peptides studied strongly depend on the temperature. NMR spectroscopy and molecular dynamics simulations were instrumental to verify the conformational preferences of three peptides. The absence of likely or oppositely charged groups at the ends of a short chain fragment destroys chain reversal because the charged groups probably screen the nonpolar core from the solvent. ITC experiment was used to study the interactions with Cu(II) ions. It was found that the most stable complexes with Cu2+ ions are formed with peptide 2, which has the most bent conformation.

The crystal structure of 2,2′-bipyridyl(iminodiacetato)oxidovanadium(IV) dihydrate of [VO(IDA)bipy]·2H2O molecular formula was redetermined. The vanadium atom has an octahedral coordination. The IDA ligand adopts the facial conformation in VO(IDA)bipy. The stability of title compound in aqueous solutions was investigated by using the potentiometric titration method. Furthermore, the kinetics of substitution reactions of the [VO(IDA)H2O]H2O binary complex with 2,2′-bipyridine was investigated in aqueous solutions. These reactions were monitored spectrophotometrically using the stopped-flow method at 260 nm. The kinetic measurements were performed in the 293–308 K temperature range, at different concentrations in the 0.1–0.5 mM range of the binary complex and at the constant concentration of bipy (0.05 mmol/L). The antioxidant properties of [VO(IDA)bipy]·2H2O and [VO(IDA)H2O]H2O complexes have been studied. The antioxidant activity of these complexes against the superoxide radical as well as stable organic radicals, namely 1,1-diphenyl-2-picrylhydrazyl radical (DPPH ) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical was investigated. The evaluation of [VO(IDA)bipy]·2H2O as a potential antioxidant agent shows that the titled complex exhibit the antioxidant activity against the superoxide anion and organic radicals.

The kinetics of substitution reactions of the CuODA and CuTDA binary complexes (ODA = oxydiacetate, TDA = thiodiacetate) with 1,10-phenanthroline (phen) and 2,2’-bipyridine (bipy) were studied in aqueous and DMSO solutions. These reactions were monitored spectrometrically using the stopped-flow method in the UV range. The studies were carried out at three temperatures - 298.15, 303.15 and 308.15 K. The concentrations of the binary complexes were kept within the range of 0.2–0.5 mmol L−1, whereas the concentration of phen or bipy was constant = 0.05 mmol L−1. The values of the reaction rate constants were calculated based on the A → B reaction model. A linear relationship of the rate of the substitution reaction versus the concentration of the binary complex as well as temperature was observed. The impact of the type of the primary (ODA and TDA) and auxiliary ligands (phen and bipy) as well as the effect of solvent on the rate of substitution reaction have been discussed.

In the following paper, we present the results of our studies on the interactions of the A&beta, 1-42 peptide and its three short fragments, namely A&beta, 5-16 (RHDSGYEVHHQK, HZ1), A&beta, 8-13 (SGYEVH, HZ2), and A&beta, 8-12 (SGYEV, HZ3) with selected painkillers (ibuprofen and aspirin) and compounds of natural origin (anabasine and epinephrine). Steady-state fluorescence spectroscopy was used to study the binding properties of the selected systems. Additionally, based on molecular dynamics (MD) calculations supported by NMR-derived restrains, we have proposed the most likely area of the interactions of A&beta, 1-42 and A&beta, 5-16 peptides with the investigated compounds. The influence of symmetrically oriented side chains of amino acid residues present in the first part of the A&beta, 1-42 sequence on the stability of the resulting complexes has been discussed. Finally, the changes in the peptide structures on account of complex formation were analyzed.

Matrix metalloproteinases (MMPs) are extracellular matrix degradation factors, promoting cancer progression. Hence, they could provide an enzyme-assisted delivery of doxorubicin (DOX) in cancer treatment. In the current study, the intercalation process of DOX and tetrapeptide&ndash, DOX, the product of the MMPs&rsquo, cleavage of carrier-linked DOX, into dsDNA was investigated using stationary and time-resolved fluorescence spectroscopy, UV-Vis spectrophotometry and isothermal titration calorimetry (ITC). The molecular dynamics (MD) simulations on the same tetrapeptide&ndash, DOX&hellip, DNA and DOX&hellip, DNA systems were also performed. The undertaken studies indicate that DOX and tetrapeptide&ndash, DOX can effectively bond with dsDNA through the intercalation mode, however, tetrapeptide&ndash, DOX forms less stable complexes than free DOX. Moreover, the obtained results demonstrate that the differences in DNA affinity of both forms of DOX can be attributed to different intercalation modes. Tetrapeptide&ndash, DOX shows a preference to intercalate into DNA through the major groove, whereas DOX does it through the minor one. In summary, we can conclude that the tetrapeptide&ndash, DOX intercalation to DNA is significant and that even the lack of non-specific proteases releasing DOX from the tetrapeptide conjugate, the presence of which is suggested by the literature for the efficient release of DOX, should not prevent the cytostatic action of the anthracycline.

The effects of arginine residues in peptide sequences on their specific acid-base properties were investigated. Two short original fragments of the human Pin1 WW domain (hPin1 14–24; hPin1 15–23) and one single point mutation system (the original charged Lys14 and Tyr24 residues were replaced with nonpolar alanine residues) derived from hPin1 were considered. The amino acid composition controls to a large extent the process of folding and thus regulates the functions of the entire system. The specific behavior of arginine residues presented in the investigated peptides in a solution is directly reflected in their abnormally low values of pKa as compared to those of the reference compound. This phenomenon seems to result from the formation of aggregates within the system by the guanidine forms present in the Arg sidechains. The acid-base properties of the investigated peptides show that under physiological conditions, the charge of these systems is close to 2. Summarizing, the analysis of interactions between peptides and biologically important structures and membranes should consider cationic forms of peptides.

Metal binding properties of histaminol (4(5)-(2-hydroxyethyl)imidazole)-natural imidazole derivative – towards several metal ions were investigated in aqueous solution and solid state. Potentiometric titrations returned stability constants for the title histaminol complexes. The stability of the investigated complexes was compared to analogous complexes with 1H-imidazole and histamine ligands. The ability of histaminol to form chelate complexes and a high tendency to occur in this role in complex compounds has been confirmed by the isolation of some of the complex species in the monocrystalline form and X-ray diffraction measurements. Solid state studies allowed further identification of the important complex species and the comparison of geometrical parameters of metal-histaminol binding for various, biologically relevant metal cations.

Herein, we have investigated principally with the use of UV and fluorescence (steady-state and time-resolved) spectroscopy the interactions between selected pentapeptides with tyrosine residue (EYHHQ, EHYHQ, EHHQY, and KYHHE) and various metal ions (Cu2+, Mn2+, Co2+, Ni2+, Zn2+, Cr3+, Cd2+, Ag+, Pb2+, Sr2+, Ba2+, Ca2+, Mg2+, Al3+, Fe2+, and Ga3+) in order to establish the relationship between the position of a tyrosine residue in the peptide sequence and the metal ion-binding properties. Among the peptides studied, EHYHQ was evaluated as an efficient and selective ligand for developing a chemosensor for the detection of copper(II) ions. While significant fluorescence emission quenching was observed for that peptide in the presence of Cu2+ cations, other metal cations used at the same and at considerably higher concentrations caused a negligible change of the fluorescence emission spectrum, indicating a high selectivity of EHYHQ for Cu2+ ions. Under optimum conditions, fluorescence intensity was inversely proportional to the concentration of Cu2+ ions. The limit of detection of Cu2+ ions with the use of EHYHQ was determined at the level of 26.6 nM. The binding stoichiometry of the complexes of the studied peptides with Cu2+ ions was evaluated spectrophotometrically and fluorimetrically (as in the case of EHYHQ confirmed by mass spectrometry) and found to be 1:2 (Cu2+-peptide) for all the investigated systems. Furthermore, the stability constant (K) values of these complexes were determined. The reversibility of the proposed Cu2+ ions sensor was confirmed, the pH range where the sensor acts was determined, while its analytical performance was compared with some other reported recently fluorescent sensors. The mechanism of the interactions between EHYHQ and Cu2+ was proposed on the basis of NMR spectroscopy investigations.

In this paper, we examine antimicrobial and cytotoxic activities, self-assembly and interactions with anionic and zwitterionic membranes of short arginine-rich lipopeptides: C16-RRRR-NH2, C14-RRRR-NH2, C12-RRRR-NH2, and C16-PRRR-NH2. They show a tendency to self-assembly into micelles, but it is not required for antimicrobial activity. The membrane binding of the lipopeptides can be accompanied by other factors such as: peptide aggregation, pore formation or micellization of phospholipid bilayer. The shortening of the acyl chain results in compounds with a lower haemolytic activity and a slightly improved antimicrobial activity against Gram-positive bacteria, what indicates enhanced cell specificity. Results of coarse-grained molecular dynamics simulations indicate different organization of membrane lipids upon binding of arginine-based lipopeptides and the previously studied lysine-based ones.

Steady-state and time-resolved fluorescence spectroscopy, UV spectrophotometry and isothermal titration calorimetry techniques were used to study the coordinating properties of the 17aa peptide fragment (D17) derived from the central part of the mouse formin binding protein (FBP28 with the PDB code: 1E0L ) towards Cu2+ ions. All the measurements were run in the 2-(N-morpholino)ethanesulfonic acid buffer (20 mM, pH 6.0). Under experimental conditions the formation of the 1:1 complex of Cu2+ ions with D17 is an entropy-driven process. Cu2+ ions cause the static fluorescence quenching of the peptide studied through the formation of a non-fluorescent complex. Furthermore, the thermal stability of D17 was discussed based on the results obtained from differential scanning fluorimetry (nanoDSF) data.

BACKGROUND AND OBJECTIVES: There is no consensus on optimal treatment duration for propranolol in infantile hemangioma (IH). We evaluated the efficacy and safety of oral propranolol solution administered for a minimum of 6 months up to a maximum of 12 months of age in high-risk IH. METHODS: This single-arm, open-label, phase 3 study was conducted in patients aged 35 to 150 days with high-risk IH in 10 hospitals between 2015 and 2017. The study comprised a 6-month initial treatment period (ITP) plus continuation up to 12 months of age if complete success was not achieved, a follow-up, and a retreatment period. Patients received oral propranolol twice daily (3 mg/kg per day). The primary end point was the success rate at the end of the ITP. Furthermore, the persistence of IH response and efficacy of retreatment was evaluated. RESULTS: The success rate after 6 months of treatment was 47%, increasing to 76% at the end of the ITP. Of the patients who achieved success, 68% sustained success for 3 months without treatment, and 24% required retreatment. Of the 8 patients who were retreated, 7 achieved success. Adverse events, reported by 80% of patients, were mild, which were expected in this population or known propranolol side effects. CONCLUSIONS: Oral propranolol administered beyond 6 months and up to 12 months of age meaningfully increases the success rate in high-risk IH. Success was sustained in most patients up to 3 months after stopping treatment. Retreatment was efficacious, and the safety profile satisfactory.