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[Display omitted] • The nitrogen-doped (N-doped) negatively charged carbon dots (TPP-CDs) without metal doping showed excellent biocompatibility. • The TPP-CDs is simple to prepare, low cost, and the purification efficiency of TPP-CDs was greatly improved by using sephadex G-50 column. • The TPP-CDs exerted dual antibacterial and anti-inflammatory activities through multiple mechanisms, achieving one-stop treatment to accelerate wound healing. • The TPP-CDs showed excellent antibacterial activity against S. aureus and E. coli without detectable resistance. The development of bacterial resistance significantly contributes to the persistence of infections. Although previous studies have highlighted the benefits of metal-doped positive carbon nanodots in managing bacterial wound infections, their mechanism of action is relatively simple and they may pose potential hazards to human cells. Therefore, it is essential to develop a one-stop carbon dot nanoplatform that offers high biocompatibility, antibacterial properties, and anti-inflammatory activities for wound infection management. This study explores the antibacterial efficacy, without detectable resistance, and wound-healing potential of nitrogen-doped (N-doped) negatively charged carbon dots (TPP-CDs). These carbon dots are synthesized using tannic acid (TA), polyethylene polyamine, and polyethylene glycol (PEG) as precursors, with a focus on their biocompatibility. Numerous systematic studies have shown that TPP-CDs can effectively destroy bacterial biofilms and deoxyribonucleic acid (DNA), while also inducing oxidative stress, leading to a potent antimicrobial effect. TPP-CDs also demonstrate the ability to scavenge excess free radicals, promote cellular proliferation, and inhibit inflammatory factors, all of which contribute to improved wound healing. TPP-CDs also demonstrate favorable cell imaging capabilities. These findings suggest that N-doped negatively charged TPP-CDs hold significant potential for treating bacterial infections and offer practical insights for their application in the medical field. [ABSTRACT FROM AUTHOR]

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BACKGROUND: Manganese (Mn) is an essential micronutrient for plants, whereas excess Mn(II) in soils leads to its toxicity to crops. Mn(II) is adsorbed onto plant roots from soil solution and then absorbed by plants. Root charge characteristics should affect Mn(II) toxicity to crops and Mn(II) uptake by the roots of the crops. However, the differences in the effects of root surface charge on the uptake of Mn(II) among various crop species are not well understood. RESULTS: The roots of nine legumes and six non‐legume poaceae were obtained by hydroponics and the streaming potential method and spectroscopic analysis were used to measure the zeta potentials and functional groups on the roots, respectively. The results indicate that the exchangeable Mn(II) adsorbed by plant roots was significantly positively correlated with the Mn(II) accumulated in plant shoots. Legume roots carried more negative charges and functional groups than non‐legume poaceae roots, which was responsible for the larger amounts of exchangeable Mn(II) on legume roots in 2 h and the Mn(II) accumulated in their shoots in 48 h. Coexisting cations, such as Ca2+ and Mg2+, were most effective in decreasing Mn(II) taken up by roots and accumulated in shoots than K+ and Na+. This was because Ca2+ and Mg2+ could compete with Mn(II) for active sites on plant roots more strongly compared to K+ and Na+. CONCLUSION: The root surface charge and functional groups are two important factors influencing Mn(II) uptake by roots and accumulation in plant shoots. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Most of cell penetrating peptides (CPPs) are rich in positively‐charged amino acids but the cationic property may provoke possible problems in practical applications. In this study, we carefully substituted the hydrophobic amino acids in the SAP(E) sequence, a rare example of negatively‐charged proline‐rich CPP, with cysteine for enhancement of cell penetrating activity as well as reversible conjugation of cargo molecules. Most substituents showed almost negligible cell penetrating activity, but a cysteine substituent on the 7th valine (SAP(E)‐7C) showed more improved cell penetrating activity than SAP(E). When treated to cells, the negatively‐charged SAP(E)‐7C exhibited much lower degree of co‐localization with acidic endosomes or lysosomes compared to positively‐charged TAT. SAP(E)‐7C could significantly enhance the PTX efficacy on MDA‐MB‐231 cells by non‐covalent complexation with PTX. As a proof‐of‐concept for covalent conjugation of cargo drugs, mercaptoethanol, a model drug, was conjugated to the cysteine residue of SAP(E)‐7C via a disulfide bond, and the glutathione‐dependent release from the conjugate was confirmed. The negatively‐charged SAP(E)‐7C with a cysteine handle can be a useful molecular module for the development of CPP‐based drug delivery carrier. [ABSTRACT FROM AUTHOR]

Mining activity may potentially produce acid mine drainage (AMD), which has relatively high acidity and dissolved heavy metal concentrations. Constructed wetlands is one of the AMD management methods in which organic matter (OM) plays a very important function in reducing the concentration of heavy metals in AMD through absorption and precipitation processes. Three types of OM (empty fruit bunches of oil palm, chicken manure and water hyacinth) and five levels of OM (0, 10, 20, 30 and 40 Mg ha-1) were applied to reclaimed-mining soils (RMS) in an incubation study. A batch experiment was then performed to measure the effect of OM application on the maximum sorption capacity (Qmax) of iron (Fe) from the AMD onto the mixed soil-OM. The application of OM resulted in increases in soil pH, carboxylic groups, and total functional groups, in which these increases varied based on the types and amounts of OM application. This study also revealed that OM application resulted in increasing Fe sorption. The application of OM increased Qmax values from 2077 to 2348-3259 mg kg-1 (water hyacinth), to 2607-3635 mg kg-1 (chicken manure), and to 2219-2992 mg kg-1 (empty fruit bunches of oil palm). Increasing these Qmax values may ascribe to increasing functional groups of the RMS with OM application. The results prove the importance of OM in controlling the sorption of Fe from AMD onto soils.

Nanozymes are particles with diameters in the range of 1–100 nm, which has been widely studied due to their biological enzyme-like properties and stability that natural enzymes do not have. In this study, several reducing agents with different structures (catechol (Cc), hydroquinone (Hq), resorcinol (Rs), vitamin C (Vc), pyrogallic acid (Ga), sodium citrate (Sc), sodium malate (Sm), and sodium tartrate (St)) were used to prepare colloidal gold with a negative charge and similar particle size by controlling the temperature and pH. The affinity analysis of the substrate H2O2 and TMB showed that the order of activities of colloidal gold Nanozymes prepared by different reducing agents was Cc, Hq, Rs, Vc, Ga, Sc, Sm, St. It was also found that the enzyme activity of colloidal gold reduced by benzene rings is higher than that of the colloidal gold enzyme reduced by linear chains. Finally, we discussed the activity of the colloidal gold peroxidase based on the number and position of isomers and functional groups; and demonstrated that the nanozymes activity is affected by the surface activity of colloidal gold, the elimination of hydroxyl radicals and the TMB binding efficiency.

Cancer, a widespread and lethal disease, necessitates precise therapeutic interventions to mitigate its devastating impact. While conventional chemotherapy remains a cornerstone of cancer treatment, its lack of specificity towards cancer cells results in collateral damage to healthy tissues, leading to adverse effects. Thus, the quest for targeted strategies has emerged as a critical focus in cancer research. This review explores the development of innovative targeting methods utilizing novel drug delivery systems tailored to recognize and effectively engage cancer cells. Cancer cells exhibit morphological and metabolic traits, including irregular morphology, unchecked proliferation, metabolic shifts, genetic instability, and a higher negative charge, which serve as effective targeting cues. Central to these strategies is the exploitation of the unique negative charge characteristic of cancer cells, attributed to alterations in phospholipid composition and the Warburg effect. Leveraging this distinct feature, researchers have devised cationic carrier systems capable of enhancing the specificity of therapeutic agents towards cancer cells. The review delineates the underlying causes of the negative charge in cancer cells and elucidates various targeting approaches employing cationic compounds for drug delivery systems. Furthermore, it delves into the methods employed for the preparation of these systems. Beyond cancer treatment, the review also underscores the multifaceted applications of cationic carrier systems, encompassing protein and peptide delivery, imaging, photodynamic therapy, gene delivery, and antimicrobial applications. This comprehensive exploration underscores the potential of cationic carrier systems as versatile tools in the fight against cancer and beyond. [Display omitted] • Negatively charged cancer cells. • Cationic nanocarriers for targeting negatively charged cancer cells. • Cationic lipids, polymers and surfactants for formulating cationic nanocarriers. • Recent research on developing cationic nanocarriers. • Various other applications of cationic nanocarries. [ABSTRACT FROM AUTHOR]

The expansion of various industries, such as the textile industry in the world, has led to the production of dye wastewater, which has caused a lot of pollution and damage to the environment. Therefore, the use of efficient methods such as nanofiltration to treat these wastewaters is one of the most important issues related to the environment. In the present study, in order to prepare the nanofiltration membrane by interfacial polymerization method, piperazine, and toluene diisocyanate monomers in the aqueous and organic phases were used. κ-Carrageenan biopolymer was used in the process of membrane modification to increase the hydrophilicity of the membrane surface and enhance a negative surface charge on it and thus improve the performance of the final membrane in removing anionic pollutes. After preparing nanofiltration membranes, they were tested to remove the anionic dyes. The results showed that the presence of κ-Carrageenan increased the hydrophilicity of the membrane surface and ultimately increased the flux of the membrane, and at the same time not only did not reduce the rejection of the anionic dyes, but increased somewhat. Finally, scanning electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, contact angle, and zeta potential analyzes were used. The results obtained by measuring contact angle confirmed hydrophilicity increase of the membrane surface in the presence of κ-Carrageenan and approved negative surface charge by measuring zeta potential. [ABSTRACT FROM AUTHOR]

BACKGROUND: Photocross linked alginate hydrogel has been a popular bone tissue engineering material because of its excellent biocompatibility and minimally invasive injection, but there are still problems such as insufficient strength and poor cell adhesion. OBJECTIVE: To construct the negatively charged hydrogels by introducing sodium methacrylate into photocrosslinked alginate hydrogels, and to explore the changes in its physical performance and cell adhesion. METHODS: After preparation of methacrylated alginate by reacting sodium alginate with 2-aminoethyl melhacrylate, methacrylated alginate, photoinitiator and sodium methacrylate (0, 20, 40, 60 mmol/L) were homogeneously mixed. The negatively charged photocrosslinked alginate hydrogels were prepared under ultraviolet light. The functional groups of the hydrogels were analyzed by fourier transform infrared spectroscopy. The surface morphology of the hydrogels was observed by scanning electron microscopy and the swelling ratio was measured. MC3T3-E1 cells were cultured with each group of hydrogels for 48 hours, and the cytotoxicity of the hydrogels was investigated by cell counting kit-8assay. MC3T3-E1 cells were seeded on the surface of each group of hydrogels. The early adhesion of the cells was observed by live/dead staining at the 4th hour, and cell spreading was observed on the 3thday. RESULTS AND CONCLUSION: (1) Fourier transfom infrared spectroscopy demonstrated that the introduction of sodium methacrylate could lead to a new peak at wavenumber of about 1600 cm-1 in the hydrogel infrared wave, which was from the sodium methacrylate. (2) Scanning electron microscope observed that the density of the negatively charged photocrosslinked alginate hydrogels increased and the pore size of the gels decreased with augment of concentrations of sodium methacrylate. (3) The swelling ratio of the hydrogel decreased with the increase of the concentration of sodium methacrylate. (4) The live/dead staining revealed that the cells grew well on the surface of each hydrogel, and the cell viability reached above 95%. The cell counting kit-8 assay results showed that the negatively charged photocrosslinked alginate hydrogels had no cytotoxicity. (5) The early cell adhesion rate increased gradually and the cell extension became better with the increase of concentration of sodium methacrylate. (6) In summary, the introduction of sodium methacryl into pholocrosslinked alginate hydrogels can adjust its physical properties and significantly improve its cell adhesion. [ABSTRACT FROM AUTHOR]

Little is known about the exact mechanism of cadmium (Cd) immobilization by phosphate (P) in arable soil containing low Cd concentration. This study was designed to describe this mechanism in detail. We determined the phosphorus (P) addition rate allowing Cd to precipitate as Cd minerals in Cd-contaminated arable soils and identified the main species of Cd minerals formed by the reaction of Cd and P, using the chemical equilibrium model MINTEQ. To determine the amount of Cd adsorption to soil adsorbed P, 0 –10,000 mgPL−1 of K2HPO4 solution was reacted with soil, then the P adsorbed soil was reacted with a CdCl2 solution (500 mg Cd L−1). Cadmium might not precipitate as Cd minerals such as Cd3(PO4)2 and CdCO3 with a recommended application rate of P fertilizer in field scale. Cadmium might be immobilized by Cd2+ adsorption instead of precipitation under a low P application system. Phosphate adsorption increased the negative charge of soil and Cd adsorption. The contributions of the increase in pH- and P-induced negative charges to the total increase in the soil negative charge were 93.2 and 6.8%, respectively. The increase in Cd adsorption caused by P adsorption was mainly attributed to the increase in pH-induced negative charge. [ABSTRACT FROM AUTHOR]

Bacteria undergo adaptive morphological changes to survive under stress conditions. The present work documents the morphological changes in Mycobacterium tuberculosis (Mtb) cells cultured under hypoxic condition using Wayne’s in vitro hypoxia model involving non-replicating persistence stages 1 and 2 (NRP stage 1 and NRP stage 2) and reveals their physiological significance. Transmission electron microscopy of the NRP stage 2 cells showed uneven but thick outer layer (TOL), unlike the evenly thin outer layer of the actively growing mid-log phase (MLP) cells. On the contrary, the saprophytic Mycobacterium smegmatis NRP stage 2 cells lacked TOL. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the Mtb NRP stage 2 cells confirmed the rough uneven surface unlike the smooth surface of the MLP cells. Zeta potential measurements showed high negative charge on the surface of NRP stage 2 cells and polysaccharide specific calcofluor white (CFW) staining of the cells revealed high content of polysaccharide in the TOL. This observation was supported by the real-time PCR data showing high levels of expression of the genes involved in the synthesis of sugars, such as trehalose, mannose and others, which are implicated in polysaccharide synthesis. Experiments to understand the physiological significance of the TOL revealed restricted entry of the biologically low-active 5-carboxyfluorescein-rifampicin (5-FAM-RIF), at concentrations equivalent to microbicidal concentrations of the unconjugated biologically active rifampicin, into the NRP stage 2 cells, unlike in the MLP cells. Further, as expected, mechanical removal of the TOL by mild bead beating or release of the NRP stage 2 cells from hypoxia into normoxia in fresh growth medium also significantly increased 5-FAM-RIF permeability into the NRP stage 2 cells to an extent comparable to that into the MLP cells. Taken together, these observations revealed that Mtb cells under hypoxia develop TOL that helps in restricting rifampicin entry, thereby conferring rifampicin tolerance.

Cyclodextrin glycosyltransferases (CGTases) are widely used in starch deep processing, so reducing their cost by improving their production is of significant industrial interest. The CGTase from Bacillus stearothermophilus NO2 possesses excellent catalytic properties but suffers from low production in E. coli. In this study, directed evolution was used to create three point mutants (I631T, I641T and K647E) that were produced in E. coli with shake-flask yields 1.7-, 2.1-, and 2.2-fold higher than that of wild-type, respectively. The wild-type and K647E were then produced in a 3-L fermenter. The CGTase activity of the K647E (1904 U mL-1) was 2.0-fold higher than that of the wild-type. The K647E fermentation supernatant could be used directly to prepare 2-O-α-d-glucopyranosyl-l-ascorbic acid, reducing the costs associated with its production. Structural modeling of the three mutants suggested that hydrophilicity, hydrogen bonding, and negative charge may be responsible for their improved production. Since K647 is conserved in the CGTase family, the corresponding residues in the CGTases from Bacillus circulans 251, Paenibacillus macerans, and Anaerobranca gottschalkii were changed to glutamic acid. Productions of the resulting K647E mutants were 2.0-, 1.5-, and 1.0-fold higher than those of their respective wild-types. Electrostatic protein surface analysis suggested that mutations occurring at low negative surface charge may increase CGTase production. [ABSTRACT FROM AUTHOR]

Bacteria undergo adaptive morphological changes to survive under stress conditions. The present work documents the morphological changes in Mycobacterium tuberculosis (Mtb) cells cultured under hypoxic condition using Wayne's in vitro hypoxia model involving non-replicating persistence stages 1 and 2 (NRP stage 1 and NRP stage 2) and reveals their physiological significance. Transmission electron microscopy of the NRP stage 2 cells showed uneven but thick outer layer (TOL), unlike the evenly thin outer layer of the actively growing mid-log phase (MLP) cells. On the contrary, the saprophytic Mycobacterium smegmatis NRP stage 2 cells lacked TOL. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the Mtb NRP stage 2 cells confirmed the rough uneven surface unlike the smooth surface of the MLP cells. Zeta potential measurements showed high negative charge on the surface of NRP stage 2 cells and polysaccharide specific calcofluor white (CFW) staining of the cells revealed high content of polysaccharide in the TOL. This observation was supported by the real-time PCR data showing high levels of expression of the genes involved in the synthesis of sugars, such as trehalose, mannose and others, which are implicated in polysaccharide synthesis. Experiments to understand the physiological significance of the TOL revealed restricted entry of the biologically low-active 5-carboxyfluorescein-rifampicin (5-FAM-RIF), at concentrations equivalent to microbicidal concentrations of the unconjugated biologically active rifampicin, into the NRP stage 2 cells, unlike in the MLP cells. Further, as expected, mechanical removal of the TOL by mild bead beating or release of the NRP stage 2 cells from hypoxia into normoxia in fresh growth medium also significantly increased 5-FAM-RIF permeability into the NRP stage 2 cells to an extent comparable to that into the MLP cells. Taken together, these observations revealed that Mtb cells under hypoxia develop TOL that helps in restricting rifampicin entry, thereby conferring rifampicin tolerance. [ABSTRACT FROM AUTHOR]

To enhance hexavalent chromium (Cr(VI)) removal performance under acidic conditions, the nanofiltration (NF) membrane with enhanced negative charge was fabricated via introducing 2, 5-diaminobenzenesulfonic acid (DABSA) into polyamide layer. The control membrane (NF-P) was directly prepared from piperazine and 1, 3, 5-benzenetricarbonyltrichloride. Surface chemical compositions, morphology, surface charge, pore size, permeability and pH-dependent separation performance of the fabricated membranes were characterized. The membranes showed the similar water permeance (∼11.5 L m-2 h−1 bar−1) and Na 2 SO 4 rejections (∼98%) under neutral environments. The DABSA introduced NF membrane (NF-PD) was negatively charged in the pH range of 2.5–11, while the isoelectric point for NF-P was ∼pH 4.0. Cr(VI) removal ability was then evaluated under various concentrations and pH environments. The results indicated that NF-PD showed the better Cr(VI) rejection performance in all tested conditions than NF-P, especially under acidic environments (e.g., pH 4 and pH 5). Moreover, there was a fluctuation of the rejection with the increase of Cr(VI) concentration under acidic environments, which was mainly caused by the formation of Cr 2 O 7 2− species. The harmful Cr(VI) was efficiently removed by the NF membrane with enhanced negative charge under acidic environments, which indicated the wider application range of the NF membrane. [ABSTRACT FROM AUTHOR]

The chemistry of NHC core pincer ligands of LX2 type bearing two pending arms, identical or not, whose coordinating center is anionic in nature, is here reviewed. In this family, the negative charge of the coordinating atoms can be brought either by a carbon atom via a phosphonium ylide (R3P+–CR2−) or by a heteroatom through amide (R2N−), oxide (RO−), or thio(seleno)oxide (RS−, RSe−) donor functionalities. Through selected examples, the synthetic methods, coordination properties, and applications of such tridentate systems are described. Particular emphasis is placed on the role of the donor ends in the chemical behavior of these species.

Political identity and political identification of One Russia and the president Władimir Putin The author of this article undertakes attempts of determination what the political identity is, indicating also similarity between this term and the term with social, national identity. By analyzing the similarity between the Polish and Russian languages the author claims that it results from a wrong interpretation of a term „identity” as well as from the process of identifying which accompanies it. In a practical part of the article the author examines an electoral program of One Russia and speeches of the president Putin in order to name values important for them and to determine their political identity. By naming linguistic means which are used by the examined parties the author concludes that they have one common political identity which is based on conservative values. The author also presents a thesis that one political identity which would be common for the Russian nationality does not exist.

In this study, the relationship between the dissociation of κ-casein from casein micelles due to heatinduced denaturation and the strength of acid milk gel was investigated. The κ-casein-dissociated micelles were fractionated by gel filtration chromatography and two-dimensional polyacrylamide gel electrophoresis, and their zeta potential and surface hydrophobicity were measured. The negative charge of the κ-casein-dissociated micelles was lower than that of native micelles, and micellar surface hydrophobicity was higher. For confirmation, the isoelectric point of the casein micelles was measured. The κ-casein-dissociated micelles were found to cohere at an earlier stage of acidification than the native micelles. These results demonstrated that the heat-induced increase in the strength of acid milk gel was partly due to the decrease in micellar surface charge and partly to the increase in surface hydrophobicity caused by the dissociation of κ-casein. [ABSTRACT FROM AUTHOR]

Aggregation of amyloid β-proteins (Aβ) induced by Cu 2 + is a crucial element in the pathogenesis of Alzheimer's disease (AD), and cerebral acidosis is a common complication of AD. Under mildly acidic conditions, Cu 2 + -Aβ species have higher tendency to generate neurotoxic aggregates. Hence it is of significance to develop potent agents that inhibit Cu 2 + -mediated Aβ aggregation under a mildly acidic condition. Herein we synthesized acidulated human serum albumin (A-HSA) to mitigate Cu 2 + -mediated Aβ 42 aggregation and cytotoxicity at pH 6.6. Extensive experiments showed that A-HSA altered the pathway of Cu 2 + -mediated Aβ 42 aggregation and protected SH-SY5Y cells from cytotoxicity and oxidative damage induced by Cu 2 + -Aβ 42 species. Equimolar A-HSA increased cell viability from 52% to 91% as compared to Cu 2 + -Aβ 42 -treated group. Stopped-flow fluorescence analysis revealed that A-HSA changed the Cu 2 + -Aβ 42 coordination mode from component I to II on the second timescale at pH 6.6, which avoided the formation of aggregation-prone Cu 2 + -Aβ 42 aggregates. The findings revealed that the more negative charges on A-HSA surface could stabilize the protonated form of the adjacent histidine residues of Aβ 42 . Hence, component I, which is necessary to form toxic aggregates, became unstable in the presence of A-HSA. On the other hand, hydrophobic binding and electrostatic repulsion could work simultaneously on the bound Aβ 42 on A-HSA surface. The two opposite forces stretched Aβ 42 conformations, which inhibited the formation of toxic Cu 2 + -Aβ 42 aggregates. Thus, A-HSA worked as a bifunctional inhibitor against Cu 2 + -mediated Aβ 42 aggregation and cytotoxicity under a mildly acidic condition. [ABSTRACT FROM AUTHOR]

Introduction Radiolabeled octreotide derivatives have been studied as diagnostic and therapeutic agents for somatostatin receptor-positive tumors. To prevent unnecessary radiation exposure during their clinical application, the present study aimed to develop radiolabeled peptides which could reduce radioactivity levels in the kidney at both early and late post-injection time points by introducing a negative charge with an acidic amino acid such as L -aspartic acid (Asp) at a suitable position in 111 In-DTPA-conjugated octreotide derivatives. Methods Biodistribution of the radioactivity was evaluated in normal mice after administration of a novel radiolabeled peptide by a counting method. The radiolabeled species remaining in the kidney were identified by comparing their HPLC data with those obtained by alternative synthesis. Results The designed and synthesized radiolabeled peptide 111 In-DTPA- d -Phe −1 -Asp 0 - d -Phe 1 -octreotide exhibited significantly lower renal radioactivity levels than those of the known 111 In-DTPA- d -Phe 1 -octreotide at 3 and 24 h post-injection. The radiolabeled species in the kidney at 24 h after the injection of new octreotide derivative represented 111 In-DTPA- d -Phe-OH and 111 In-DTPA- d -Phe-Asp-OH as the metabolites. Their radiometabolites and intact 111 In-DTPA-conjugated octreotide derivative were observed in urine within 24 h post-injection. Conclusion The present study provided a new example of an 111 In-DTPA-conjugated octreotide derivative having the characteristics of both reduced renal uptake and shortened residence time of radioactivity in the kidney. It is considered that this kinetic control was achieved by introducing a negative charge on the octreotide derivative thereby suppressing the reabsorption in the renal tubules and affording the radiometabolites with appropriate lipophilicity. [ABSTRACT FROM AUTHOR]

In spite of high-throughput phosphoproteomics for protein kinase-phosphorylation site interactions, the evolutionary mechanism for the origin of protein phosphorylation remains a mystery. Pearlman and his colleagues proposed that some phosphorylation sites may have evolved from acidic amino acids, because those negatively charged amino acids (Asp/Glu) can mimic the phosphorylated state of a protein. Moreover, phosphorylation has the potential to conditionally restore the salt bridge that was originally constitutively formed by Asp/Glu. Although this insightful mimic hypothesis has been supported by several examples, we point out that the replacements from Asp/Glu to serine/threonine require at least two non-synonymous nucleotide substitutions, casting some doubt about whether it is the major mechanism for the origin of phosphorylation. As the intermediate amino acid types, such as Ala/Asn/Gly, are not observed frequently, we have to invoke the hypothesis of double-mutation driven by natural selection; that is, the very strong positive selection for the second mutation has overcome the deleterious effect caused by the first mutation. Furthermore, we propose an alternative evolutionary scenario that phosphorylation was primarily evolved to introduce negative charges to the protein surface, thus reducing spurious protein-protein interactions in vivo by electrostatic repulsion. The specific protein-protein interaction could be regulated when corresponding signals change surface charges by means of dephosphorylation and other recognition mechanisms. Probably this is a more universal mechanism that provided the first step toward the emergence of more accurate cell signaling and regulation. Further study is needed to distinguish between these hypotheses. [ABSTRACT FROM AUTHOR]

A negatively charged hydrophilic low fouling film was prepared by thermally cross-linking a blend consisting of polystyrene sulfonic acid (PSS) and polyethylene glycol (PEG). The film was found to be stable by dip-washing. The fouling resistance of this material toward bacterial ( Escherichia coli ) and colloidal (polystyrene particles) attachment, non-specific protein (fibronectin) adsorption and cell (3T3 NIH) adhesion was evaluated and was compared with glass slides modified with polyethylene glycol (PEG) brushes, oxidized 3-mercaptopropyltrimethoxysilane (sulfonic acid, SA), and n -octadecyltrichlorosilane (OTS). The extended Derjaguin – Landau–Verwey–Overbeek (XDLVO) theory and thermodynamic models based on surface energy were used to explain the interaction behaviors of E. coli /polystyrene particles–substrate and protein–substrate interactions, respectively. The cross-linked PSS-PEG film was found to be slightly better than SA and PEG toward resisting non-specific protein adsorption, and showed comparable low attachment results as those of PEG toward particle, bacterial and NIH-3T3 cells adhesion. The low-fouling performance of PSS-PEG, a cross-linked film by a simple thermal curing process, could allow this material to be used for applications in aqueous environments, where most low fouling hydrophilic polymers, such as PSS or PEG, could not be easily retained. [ABSTRACT FROM AUTHOR]

Bimetallic nanostructures have received considerable attention in recent years due to their widespread use in applications such as photonics, catalysis and surface-enhanced Raman scattering (SERS) detection. In this work, a simple and effective strategy has been developed to synthesize Ag/Au@negative(COO − )-Ag/Au@positive(NH 3 + ) charge on the nanocubes’ (with hollow or porous structures) surfaces, based on a galvanic replacement reaction and co-reduction method of the corresponding ions. The prepared bimetallic Ag/Au@NH 3 + -Ag/Au@COO − nanocubes have been characterized by UV–vis, TEM, and XRD. Our results show that the SERS technique is able to detect R6G within wide concentration range, i.e. 10 -16 – 10 -8 M, with lower limit of detection (LOD) being 10 -16 M. It demonstrates that the Ag/Au@NH 3 + -Ag/Au@COO − nanocubes have potential applications in SERS for the detection of biomolecules or dye molecules. [ABSTRACT FROM AUTHOR]