Adsorption Of Glycine Research Articles

Unraveling Slurry Chemistry/Nanoparticle/Polymeric Membrane Adsorption Relevant to Cu Chemical Mechanical Planarization (CMP) Filtration Applications

Due to the emergence of sub-10 nm technologies, next generation slurries have continued to increase in complexity to meet stringent device performance demands. Prior to the chemical mechanical planarization (CMP) process, point-of-use filtration (POU) is implemented in order to limit particle aggregates and ultimately decrease surface defects. This study probes the non-covalent interactions at the interface of a fundamental Cu slurry and a polyamide and polypropylene-based membranes. Results indicate that independent of the membrane used, material removal rate (MRR) showed a subtle decrease as a result of filtration (time and ΔP), demonstrating that the synergistic balance between the nanoparticle and slurry additives is disrupted during the filtration process. Corrosion current measurements (Icorr) decreased by at least 85% post-filtration, indicating a rapid adsorption of glycine to the filter membrane. Regardless of the filter membrane, glycine adsorption was further validated using a modified electrochemical quartz crystal nanobalance (EQCN) technique. Since Cu-glycine complexes are integral in controlling MRR, a widely reported method of tracking *OH production was employed. Results show a decrease in the concentration of *OH, which in turn can be correlated to a decrease in the Cu-glycine complexes, altering the overall Cu MRR.

Destroying activity of glycine coated magnetic nanoparticles on lysozyme, α-lactalbumin, insulin and α-crystallin amyloid fibrils

Abstract A great variety of human protein deposition and protein aggregation diseases (Alzheimer’s disease, diabetes mellitus, cataract, systemic amyloidosis and other) have been associated with the accumulation of amyloid fibrils in different tissues. Therefore, development of the agents able to reduce amyloid deposits represents an attractive strategy for their treatment. We have investigated ability of glycine coated magnetic nanoparticles (Gly-MNPs) to destroy protein amyloid fibrils. The properties of Gly-MNPs were characterized with the aim to identify the optimized conditions for the glycine adsorption on surface of MNPs. It was found that Gly-MNPs have superparamagnetic behavior and their size, isoelectric point and stability depend on the amount of the glycine in the samples. The obtained results suggest that optimal weight ratio (w/w) for the modification of MNPs by glycine (Gly/Fe3O4) is equal to 5/1. The selected Gly5-MNPs1 were used for the study of their effect on amyloid fibrils of four globular proteins, namely lysozyme, bovine α-lactalbumin, insulin and α-crystallin. It was found that Gly5-MNPs1 destroy lysozyme, α-lactalbumin and insulin amyloid fibrils in concentration dependence manner. However, Gly5-MNPs1 were not able significantly destroy bovine α-crystallin amyloid fibrils. We assume that obtained results represent important contribution for rational design of potential therapeutics of amyloid diseases based on nanoparticles.

Influence of Buffer Solutions on both the Electrokinetic Potential of Multilayer Carbon Nanotubes and the Adsorption of Glycine by Them

Influence of Buffer Solutions on both the Electrokinetic Potential of Multilayer Carbon Nanotubes and the Adsorption of Glycine by Them

Aqueous oxidation of iron monosulfide (FeS) in the presence of glycine

The effect of glycine on the aqueous oxidation of FeS was evaluated in the range of 0.1–1.0mM at pH2.5 and 25°C by electrochemical techniques (potentiodynamic polarization and Electrochemical Impedance Spectroscopy) and Density Functional Theory (DFT) computations. Our findings show that the inhibition efficiency of glycine in controlling the oxidative dissolution of FeS increases when the glycine concentration increases up to 0.5mM. Further increase of glycine concentration up to 1mM produces the decrease of the corresponding inhibition efficiency. The results of our study indicate that the inhibiting effect of glycine on the oxidative dissolution of FeS is produced by the glycine adsorption on the ferric iron formed by the oxidation of the FeS surface.

Canonical, Deprotonated, or Zwitterionic? A Computational Study on Amino Acid Interaction with the TiO2 (101) Anatase Surface

The interaction of 11 amino acids with the TiO2 (101) anatase surface was investigated by means of PBE-D2* periodic simulations, both from a static and dynamic points of view. Several adsorption states, with the amino acid in its canonical, zwitterionic, or deprotonated forms, were considered. The strongest interactions correspond to dative interactions between the electron pairs of N or O atoms of the amino acids and the Ti atoms of the surface. For glycine, the most stable configuration corresponds to the deprotonated (N,O) binding mode, at variance to that observed for the adsorption of glycine on rutile (110) surface, for which the dissociative (O,O) binding mode was determined to be the preferred one. For the remaining amino acids, the following general trend was identified: those amino acids with acidic or a basic lateral chain groups, except Arg, exhibit a deprotonated (N,O) binding mode as glycine, because the additional dative interactions with the side chain overcome the destabilizing effect ind...

Adsorption of arginine, glycine and aspartic acid on Mg and Mg-based alloy surfaces: A first-principles study

Studying the adsorption behaviors of biomolecules on the surface of Mg and Mg-based alloy has a fundamental and important role for related applications in biotechnology. In the present work, we systematically investigate and compare the adsorption properties of three typical amino acids, i.e., Arg (arginine), Gly (glycine) and Asp (aspartic acid), which form RGD tripeptide, on the Mg (0001) surface with various doping (Zn, Y, and Nd), and aim to realize proper binding between biomolecules and Mg and Mg-based biomedical materials. Our results show that flat adsorption configurations of the functional groups binding to the surfaces are favored in energy for all the three selected amino acids. In specific, for the amino acids adsorped on clean Mg (0001) surface, the adsorption energy (Eads) of Arg is found to be −1.67eV for the most stable configuration, with amino and guanidyl groups binding with the surface. However, Gly (Asp) is found to binding with the surface through amino and carboxyl groups, with a −1.16eV (−1.15eV) binding energy. On the 2% Zn doped Mg (0001) alloy surface (Mg–Zn (2%)), the Eads are significantly increased to be −1.91eV, −1.32eV and −1.35eV for Arg, Gly and Asp, respectively. While the Mg–Y (1%) and Mg–Nd (1%) slightly weaken the adsorption of three amino acids. Moreover, we have performed detail discussions of the binding properties between amino acids and surfaces by projected density of states (PDOS) combined with charge transfer analyses. Our studies provide a comprehensive understanding on the interactions between amino acids and Mg and Mg-based alloy surfaces, with respect to facilitate the applications of Mg and Mg-based biomedical alloys in biosensing, drug delivery, biomolecule coating and other fields in biotechnology.

Investigation of the structural anisotropy in a self-assembling glycinate layer on Cu(100) by scanning tunneling microscopy and density functional theory calculations

Self-assembling organic molecule-metal interfaces exhibiting free-electron like (FEL) states offers an attractive bottom-up approach to fabricating materials for molecular electronics. Accomplishing this, however, requires detailed understanding of the fundamental driving mechanisms behind the self-assembly process. For instance, it is still unresolved as to why the adsorption of glycine ([NH2(CH2)COOH]) on isotropic Cu(100) single crystal surface leads, via deprotonation and self-assembly, to a glycinate ([NH2(CH2)COO–]) layer that exhibits anisotropic FEL behavior. Here, we report on bias-dependent scanning tunneling microscopy (STM) experiments and density functional theory (DFT) calculations for glycine adsorption on Cu(100) single crystal surface. We find that after physical vapor deposition (PVD) of glycine on Cu(100), glycinate self-assembles into an overlayer exhibiting c(2×4) and p(2×4) symmetries with non-identical adsorption sites. Our findings underscore the intricacy of electrical conductivity in nanomolecular organic overlayers and the critical role the structural anisotropy at molecule-metal interface plays in the fabrication of materials for molecular electronics.

A DFT study of the adsorption of glycine in the interlayer space of montmorillonite.

The adsorption properties of clay minerals have been widely studied in several technological areas, due to their versatility, absorption capacity and catalytic properties. The interaction of amino acids with clay surfaces can be interesting due to their role in prebiotic scenarios. Different degrees of hydration and the adsorption of the glycine molecule and glycinium cation in the interlayer space of montmorillonite were investigated by means of calculations based on density functional theory (DFT). Our calculations show that the cation exchange of K+ by glycinium in the interlayer of hydrated K-montmorillonite is highly possible and exothermic. This supports previous experimental results by explaining the possible adsorption of glycine as a molecule and cation. Glycine is adsorbed in a zwitterionic form in the interlayer without being solvated with water. Besides, glycine and glycinium are highly exothermically adsorbed in the interlayer. The interlayer spacings under different conditions were in agreement with the experimental values. Hydrogen bonds and electrostatic interactions between molecules and surface atoms are responsible for this exothermicity. The IR spectra were calculated and compared with the experimental results showing interesting frequency shifts depending on the intermolecular interactions in the interlayer space of montmorillonite.

Detection of Copper(II) Ions Using Glycine on Hydrazine-Adsorbed Gold Nanoparticles via Raman Spectroscopy.

A facile, selective, and sensitive detection method for the Cu2+ ions in environmental and biological solutions has been newly developed by observing the unique CN stretching peaks at ~2108 cm−1 upon the dissociative adsorption of glycine (GLY) in hydrazine buffer on gold nanoparticles (AuNPs). The relative abundance of Cu species on AuNPs was identified from X-ray photoelectron spectroscopy analysis. UV-Vis spectra also indicated that the Au particles aggregated to result in the color change owing to the destabilization induced by the GLY-Cu2+ complex. The CN stretching band at ~2108 cm−1 could be observed to indicate the formation of the CN species from GLY on the hydrazine-covered AuNP surfaces. The other ions of Fe3+, Fe2+, Hg2+, Mg2+, Mn2+, Ni2+, Zn2+, Cr3+, Co2+, Cd2+, Pb2+, Ca2+, NH4+, Na+, and K+ at high concentrations of 50 µM did not produce such spectral changes. The detection limit based on the CN band for the determination of the Cu2+ ion could be estimated to be as low as 500 nM in distilled water and 1 µM in river water, respectively. We attempted to apply our method to estimate intracellular ion detection in cancer cells for more practical purposes.

A DFT study of adsorption of glycine onto the surface of BC2N nanotube

A theoretical study of structure and the energy interaction of amino acid glycine (NH2CH2COOH) with BC2N nanotube is crucial for apperception behavior occurring at the nanobiointerface. Herein, we studied the adsorption of glycine in their radical and zwitterionic forms upon the surface of BC2N nanotube using M06 functional and 6-311G** standard basis set. We also considered the different orientations of the glycine amino acid on the surface of adsorbent. Further, we found out that the stability of glycine from its carbonyl group is higher than hydroxyl and amine groups. Our results also indicated that the electronic structure of BC2N nanotube on the adsorption of glycine from its amine group is more altered than the other groups. Our study exhibits that opto-electronic property of adsorbent is changed after the glycine adsorption.

Glycine adsorption on a mercury electrode modified by neodymium

Ranges of neodymium reduction potentials in aqueous solutions of potassium chloride at pH = 2 and in solutions containing glycine were determined by differential pulse polarography. The glycine complex with neodymium is not formed in the range of the amino acid concentration 0.001–0.12 M. Glycine adsorption on a mercury electrode and on an electrode modified with neodymium was studied by the cyclic voltammetry method.

Effects of ammonium application rate on uptake of soil adsorbed amino acids by rice

In recent years, excessive use of chemical nitrogen (N) fertilizers has resulted in the accumulation of excess ammonium (NH 4 + ) in many agricultural soils. Though rice is known as an NH 4 + -tolerant species and can directly absorb soil intact amino acids, we still know considerably less about the role of high exogenous NH 4 + content on rice uptake of soil amino acids. This experiment examined the effects of the exogenous NH 4 + concentration on rice uptake of soil adsorbed glycine in two different soils under sterile culture. Our data showed that the sorption capacity of glycine was closely related to soils;’ physical and chemical properties, such as organic matter and cation exchange capacity. Rice biomass was significantly inhibited by the exogenous NH 4 + content at different glycine adsorption concentrations. A three-way analysis of variance demonstrated that rice glycine uptake and glycine nutritional contribution were not related to its sorption capacity, but significantly related to its glycine:NH 4 + concentration ratio. After 21-d sterile cultivation, the rice uptake of adsorbed glycine accounted for 8.8%;–22.6% of rice total N uptake, which indicates that soil adsorbed amino acids theoretically can serve as an important N source for plant growth in spite of a high NH 4 + application rate. However, further studies are needed to investigate the extent to which this bioavailability is realized in the field using the 13C, 15N double labeling technology.

Adsorption of proline, hydroxyproline and glycine on anatase (001) surface: a first-principle study

The adhesion property of an implant material is heavily influenced by the interaction between implant material and protein molecules of blood or biological fluids. Collagen is a fibrous protein that plays a crucial role in the extracellular matrix and in connective tissue between organ and bone. In the present work, the first-principle calculations are used to investigate the adsorption of proline, hydroxyproline and glycine, major components of collagen protein on anatase TiO2 (001) surface. The adsorption energies are calculated using GGA with PBE functional and PBE-D2 methods. For proline, hydroxyproline and glycine, the dissociative adsorption configuration is having maximum interaction energy of −1.81 and −2.38, −1.87 and −2.52, −1.53 and −2.11 eV, respectively, at PBE and PBE-D2 methods. The above results indicate that the binding of amino acid with TiO2 is primarily through the carboxyl group. Further, this study shows that the anatase TiO2 crystals with more (001) facets will enhance the biocompatibility and osseointegration of implant material.

Graphdiyne as a promising material for detecting amino acids.

The adsorption of glycine, glutamic acid, histidine and phenylalanine on single-layer graphdiyne/ graphene is investigated by ab initio calculations. The results show that for each amino acid molecule, the adsorption energy on graphdiyne is larger than the adsorption energy on graphene and dispersion interactions predominate in the adsorption. Molecular dynamics simulations reveal that at room temperature the amino acid molecules keep migrating and rotating on graphdiyne surface and induce fluctuation in graphdiyne bandgap. Additionally, the photon absorption spectra of graphdiyne-amino-acid systems are investigated. We uncover that the presence of amino acid molecules makes the photon absorption peaks of graphdiyne significantly depressed and shifted. Finally, quantum electronic transport properties of graphdiyne-amino-acid systems are compared with the transport properties of pure graphdiyne. We reveal that the amino acid molecules induce distinct changes in the electronic conductivity of graphdiyne. The results in this paper reveal that graphdiyne is a promising two-dimensional material for sensitively detecting amino acids and may potentially be used in biosensors.

The Adsorption of Glycine in Non-Ionic and Zwitter Ionic States on Intrinsic and Functionalized Semiconducting Carbon Nanotubes

The Adsorption of Glycine in Non-Ionic and Zwitter Ionic States on Intrinsic and Functionalized Semiconducting Carbon Nanotubes

Spontaneous Local Symmetry Breaking: A Conformational Study of Glycine on Cu{311}

Understanding the interplay between intrinsic molecular chirality and chirality of the bonding footprint is crucial in exploiting enantioselectivity at surfaces. As such, achiral glycine and chiral alanine are the most obvious candidates if one is to study this interplay on different surfaces. Here, we have investigated the adsorption of glycine on Cu{311} using reflection–absorption infrared spectroscopy, low-energy electron diffraction, temperature-programmed desorption, and first-principles density-functional theory. This combination of techniques has allowed us to accurately identify the molecular conformations present under different conditions and discuss the overlayer structure in the context of the possible bonding footprints. We have observed coverage-dependent local symmetry breaking, with three-point bonded glycinate moieties forming an achiral arrangement at low coverages, and chirality developing with the presence of two-point bonded moieties at high coverages. Comparison with previous work on the self-assembly of simple amino acids on Cu{311} and the structurally similar Cu{110} surface has allowed us to rationalize the different conditions necessary for the formation of ordered chiral overlayers.

In Situ Ftirs Study of Glycine Effects on Cobalt Electrodeposition on Gold Electrodes

INTRODUCTION The presence of certain chemical species (additives) in plating baths can significantly influence the metal electrodeposition process. Thus, the electrodeposits may show different properties, due to altered morphology, structure or composition. Glycine is an additive present in many electrolytic solutions for electrodeposition of Cobalt thin films and alloys (which are interesting due to their magnetic properties). The properties of some Co-based alloys obtained from glycine-containing baths are well documented [1,2], but more fundamental-oriented studies of the exact role of the aminoacid are lacking. In this paper, we report some spectroelectrochemical studies using external reflection FTIR spectroscopy, method that can be used to obtain microscopic information on the interfacial region, assess the possibility of glycine adsorption at negative electrode potentials, and verify possible alterations in composition of solutions containing cobalt and glycine. EXPERIMENTAL The spectroelectrochemical experiments were carried out in solutions containing CoSO4 (0.050 mol L-1), Na2SO4 (0.30 mol L-1) and glycine (0.20 mol L-1), with pH values of 3, 4, and 6. A gold electrode (8 mm diameter) was used as working electrode. The electrode potentials are referred to a Ag|AgCl (3M KCl) reference electrode, which was separated from solution via Luggin capillary. The spectroelectrochemical cell had a flat CaF2window at its bottom, to which the gold electrode was pressed against. Experiments consisted of a potential step from +0.20 V (E0) to the desired sample potential (ES, with ES<E0), where spectra were acquired. The absorbance unit is given by A = -log(I/I0), with I0being the radiation intensity at the reference potential (+0.20 V). RESULTS AND DISCUSSION The hydrogen evolution reaction (HER) imposed a lower limit for the electrode potentials that could be studied. At these limit potentials, the H2evolution starts to disturb the thin layer. In our system, the potential limits were -0.55 V for pH 3, and -0.75 V for pH 6. Within these limits, no signs of adsorption of glycine on the Au electrode were detected with the experimental conditions and configuration utilized. Changes in composition of the solution in the thin layer were detected and depended on pH, as expected. For solutions in pH 3 the HER is strongly intensified in comparison to glycine-free solutions, this being attributed to appearance of a pH buffer, as a significant fraction of glycine is in the cation form (protonated carboxyl). During the potential steps, negative absorption bands assigned to the cation and positive bands assigned to the zwitterion form were observed in the spectra, confirming perturbation of the equilibrium. The use of glycine in this pH value is not common in plating baths, but may be useful in Co alloys electrodeposition according to some authors [2]. For pH 4, signs of glycine coordination to Co2+ are observed. The absorption bands assigned to symmetric and asymmetric carboxyl stretching in the zwitterion appear in lower wavenumbers when sufficiently negative potentials are applied (-0.60 V, Figure 1), this evidences complex formation [3]. In the initial pH value of 4, cobalt-glycine complexes are absent. Therefore, the increase in thin layer pH should be substantial (at least to pH 5) during electrode polarization. Similarly, in pH 6 solutions, the infrared spectra show an increase in the concentration of cobalt-glycine complexes at negative potentials. CONCLUSIONS In the range of electrode potentials investigated, glycine molecules do not undergo redox reactions, and no signs of adsorption on polycrystalline Au electrode were detected. For low pH values in which a considerable amount of glycine is in its cation form, the HER is greatly enhanced. In pH 4, the increase of pH in the thin layer during potential step to -0.60 V was high enough to promote Co2+coordination with glycine. In pH 6, a rise in the concentration of the complexes was detected, probably also due to HER. ACKNOWLEDGEMENTS We thank Professor Mauro C. dos Santos and Júlio C. M. da Silva for useful discussions. We thank Fapesp and CNPq for the financial support. REFERENCES 1. J. C. Wei, M. Schwartz e K. Nobe. J. Electrochem. Soc. 155(10), D660 (2008). 2. O. Ergeneman, K. M. Sivaraman, S. Pané, E. Pellicer, A. Teleki, A. M. Hirt, M. D. Baró, B. J. Nelson, Electrochim. Acta 56, 1399 (2011). 3. K. Nakamoto, Y. Morimoto, A. E. Martell, J. Am. Chem. Soc. 83, 4528 (1961). Figure 1

DRIFTS of Probe Molecules Adsorbed on Magnesia, Zirconia, and Hydroxyapatite Catalysts

Acid sites, base sites, and acid–base site pairs on zirconia, magnesia, and hydroxyapatite were investigated using diffuse reflectance FT-IR spectroscopy (DRIFTS) to evaluate the interaction of various adsorbed probe molecules with their surfaces. The DRIFTS spectra were recorded under continuous flow conditions at atmospheric total pressure during a temperature-programmed thermal ramp. Lewis acidity was assessed by observing the various pyridine ring mode conformations and the peak shift associated with adsorption of CO. Basicity was probed by the adsorption of CO2 to form carbonates and bicarbonates on the samples. The acid–base bifunctional nature of the oxides was explored by adsorption of acetylene and glycine. As expected, zirconia exposed the strongest Lewis acid sites of the three samples, whereas magnesia exhibited the strongest basic sites. In contrast, hydroxyapatite had a poor affinity for all probe molecules used in this study based on temperature-programmed desorption experiments, indicating...

Adsorption of RGD tripeptide on anatase (0 0 1) surface – A first principle study

An appropriate cell response to implant surface is essential for tissue integration and regeneration. The implant material is precoated with proteins such as elastin, fibronectin, vitronectin, laminin or Arg–Gly–Asp (RGD) to improve the cell adhesive properties and tissue integration and accelerated bone healing. In the present work, the first principle calculations are performed to investigate the adsorption of arginine, aspartic acid, glycine and RGD tripeptide on anatase TiO2 (001) surface. The adsorption energies are calculated using PBE, PBEsol and DFT-D2 methods. For arginine, the adsorption with anatase TiO2 is occurring through hydrogen bonds between amino groups of arginine and oxygen atom of TiO2 surface. The zwitterionic form of aspartic acid has strong interaction with anatase TiO2 (001) surface. The adsorption strength of glycine in dissociative adsorption configuration is higher than that of molecular and zwitterionic adsorption configurations. For RGD tripeptide, RGD-4 configuration is having maximum adsorption energy of −1.19, −1.46 and −1.62eV at PBE, PBEsol and DFT-D2 methods. Analysis of the electron density difference plot and Bader charge analysis shows that the carboxyl groups of aspartic acid furnish the maximum contribution for the adsorption of RGD tripeptide on TiO2.

Adsorption of glycine on diamond (001): Role of bond angle of carbon atoms**Project supported by the National Natural Science Foundation of China (Grant Nos. 51272278, 91323304, 10774177, and 11374341), the National Basic Research Program of China (Grand No. 2009CB930502), the Knowledge Innovation Project of Chinese Academy of Sciences (Grand No. KJCX2-EW-W02), the Fundamental Research Funds for the Central Universities of

The adsorption behaviors of glycine on diamond (001) are systematically investigated by first-principles calculations. We have considered all possible adsorption configurations without a surface dangling bond and give a quantitative analysis for the relationship between the deviation of carbon bond angle and adsorption energy. We found that a smaller distortion of carbon covalent bond angle results in a more stable adsorption structure, and the most stable adsorption has a benzene-ring-like structure with the highest adsorption energy of 5.11 eV per molecule and the minimum distortion of carbon covalent bond angle.