Charge transfer reactions from tryptophan and tyrosine to sulfur-centered dimer radical cation in aqueous -sulfuric acid medium: a pulse radiolysis study

Joshi, Ravi

doi:10.1002/poc.3530

Cited by 8 publications

(4 citation statements)

References 30 publications

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“…Considering the pKa values of LAC (3.86 57 ) and PLA (3.10 58 ), the deprotonated LAC/PLA form (also called LAC/PLA for short) is the dominated species in the studied pH conditions except for the simulation with pH ≈ 1.0 (Figure 1b and Figure S2). In addition, there are several kinds of anions in SBF solution, such as carbonate ions (Figure S3), whose protonation state distribution at different pH values depends on their pKa values [59][60][61] . The GAFF2 force field was used for the phosphate species, with the force field parameters shown in Table S9.…”

Section: Simulations Of Aggregation and Nucleationmentioning

confidence: 99%

“…The 500 ns MD simulations were run at NPT ensemble (with the constant pressure of 1.0 bar and temperature of 300 K) for the model systems with different pH values and Ca/P ratios, as shown in Tables S10-S15. The temperature was controlled using Langevin dynamics 61 with the collision frequency of 1 ps -1 . Integration step was set as 1 fs.…”

Section: Simulations Of Aggregation and Nucleationmentioning

confidence: 99%

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Surface Stability and Morphology of Calcium Phosphate Tuned by pH Values and Lactic Acid Additives: Theoretical and Experimental Study

Chen

Guo

et al. 2022

ACS Appl. Mater. Interfaces

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The ubiquitous mineralization of calcium phosphate (CaP) facilitates biological organisms to produce hierarchically structured minerals. The coordination number and strength of Ca 2+ ions with phosphate species, oxygen-containing additives, and solvent molecules played a crucial role in tuning nucleation processes and surface stability of CaP under the simulated body fluid (SBF) or aqueous solutions upon the addition of oligomeric lactic acid (LACn, n=1, 8) and changing pH values. As revealed by ab initio molecular dynamics (AIMD), density functional theory (DFT), and molecular dynamics (MD) simulations as well as high-throughput experimentation (HTE), the binding of LAC molecules with Ca 2+ ions and phosphate species could stabilize both pre-nucleation clusters and brushite (DCPD, CaHPO4• 2H2O) surface through intermolecular electrostatic and hydrogen bonding interactions. When the concentration of Ca 2+ ions ([Ca 2+ ]) is very low, the amount of the formed precipitation decreased with the addition of LAC based on UV-Vis spectroscopic analysis due to the reduced chance for the LAC capped Ca 2+ ions to coordinate with phosphates and the increased solubility in acid solution. With the increasing [Ca 2+ ] concentration, the kinetically stable DCPD precipitation was obtained with high Ca 2+ coordination number and low surface energy. Morphologies of DCPD precipitation are in plate, needle, or rod, depending on the initial pH values that tuned by adding NH3•H 2O, HCl, or CH3COOH. The prepared samples at pH ≈ 7.4 with different Ca/P ratios exhibited negative zeta potential values, which were correlated with the surface electrostatic potential distributions and potential biological applications.3 INTRODUCTIONBones and teeth of vertebrates are known to come from mineralization of calcium phosphate (CaP) 1 through two possible nucleation processes, i.e., a classical aggregation or a two-step nucleation pathway. 2 The real nucleation process of CaP in biological conditions becomes much more complicated, attracting extensive interest both experimentally and theoretically.The first factor in controlling nucleation process of CaP is the pH value, which could affect the occurrence of different phosphate species, such as H3PO4 (called 3H for short), H2PO4 -(2H), HPO4 2-(1H), and PO4 3-(0H), shown in Figure 1a. Thus, properties of CaP precipitation, 3, 4 adsorption of organic acid 5 , phase composition 6 , morphology 7, 8 , zeta potentials [9][10][11][12] , and crystal size of CaP 13 could be varied with different pH values.Secondly, through the modulation of interfacial interaction and kinetic stability, the introduction of many kinds of additives, such as metal ions, acid or basic solutions, amino acids, dopamine, and citrate, could change the nucleation or phase transformation paths and morphologies 8, 14-19 . Starting from the ion pair CaHPO4 in a neutral or basic CaP solution, a Ca-deficient pre-nucleation cluster, Ca(HPO4)3 4-, is formed at the early stage of nucleation process. [20][21][22][23][24] Subsequently, those sm...

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Section: Simulations Of Aggregation and Nucleationmentioning

confidence: 99%

Section: Simulations Of Aggregation and Nucleationmentioning

confidence: 99%

Surface Stability and Morphology of Calcium Phosphate Tuned by pH Values and Lactic Acid Additives: Theoretical and Experimental Study

Chen

Guo

et al. 2022

ACS Appl. Mater. Interfaces

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“…When the pH is greater than 5, they are both in deprotonated states (Figure S4). In addition, there are several kinds of anions in SBF solution, such as carbonate ions, whose protonation state distribution at different pH values depends on their pKa values [58][59][60] , as shown in Figure S5. The GAFF2 force field was used for the phosphate species, with the force field parameters shown in Table S3.…”

Section: Simulations Of Aggregation and Nucleation Of Capmentioning

confidence: 99%

Tuning Coordination Modes and Nucleation of Calcium Phosphate with Oligomeric Lactic Acid and pH Values: Theoretical and Experimental Study

Chen

Guo

et al. 2021

Preprint

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Mineralization of calcium phosphate (CaP) is ubiquitous in nature, which can facilitate biological organisms produce hierarchically structured minerals. The influences of the addition of oligomeric lactic acid (LACn, n=1, 8) and changing pH values on nucleation processes of CaP under the simulated body fluid (SBF) solution or aqueous solution were revealed by using ab initio molecular dynamics (AIMD) and molecular dynamics (MD) simulations. Through increasing pH value, the coordination between differently protonated phosphate species and Ca2+ ions could be tuned from the monodentate (η1) to the coexisting monodentate and bidentate (η2) modes. The carboxyl and hydroxyl groups of LAC molecules are capable of forming multiple interactions such as proton transfer, electrostatic interaction, and intermolecular hydrogen bonding with phosphate species and Ca2+ ions on both pre-nucleation clusters and hydroxyapatite (HA) surfaces. The high-throughput experimentations (HTE) with factors of the adding LAC, changing Ca/P ratios (1.25 ~ 2.50), using different solutions demonstrated that the UV-Vis absorbance values decreased with addition of LAC, indicating the inhibition of the nucleation process of CaP. At the physiological pH of 7.4, the CaP samples with different Ca/P ratios (1.50, 1.67 and 2.00) exhibited negative zeta potential values, which were correlated with the surface electrostatic potential distributions and potential biological applications. The precipitation was CaHPO4·2H2O (DCPD) in neutral condition at the early stage of nucleation process. Understanding the effects of different pH and Ca/P values on the nucleation process and interfacial interaction between LAC additive and the nanocluster is helpful to guide the rational design of biocompatible materials.

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“…[13][14][15][16] While the oxidation of tryptophan residues often leads to deleterious effects on protein function, 17 the oxidized form of tryptophan-either the tryptophan radical (Trp⋅) or the tryptophan radical cation (Trp⋅ + ), depending on the pH of the aqueous medium-also serves as a key intermediate in several biological processes. [18][19][20][21][22][23][24] Examples of such processes include electron transfer in DNA photolyase, [25][26][27] oxidation of cytochrome c by cytochrome c peroxidase, [28][29][30] radical transport in ribonucleotide reductase, [31][32][33] and protection of enzymes against oxidative damage during catalysis. 34,35 In addition, the tryptophan radical and radical cation also form the basis of various photochemical radical initiation schemes, [36][37][38] employed to shed light on radical formation and transport mechanisms in biological systems.…”

Section: Introductionmentioning

confidence: 99%

Observation of intra- and intermolecular vibrational coherences of the aqueous tryptophan radical induced by photodetachment

Yusof

Debnath

Loh

2021

The Journal of Chemical Physics

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The study of the photodetachment of amino acids in aqueous solution is pertinent to the understanding of elementary processes that follow the interaction of ionizing radiation with biological matter. In the case of tryptophan, the tryptophan radical that is produced by electron ejection also plays an important role in numerous redox reactions in biology, although studies of its ultrafast molecular dynamics are limited. Here, we employ femtosecond optical pump-probe spectroscopy to elucidate the ultrafast structural rearrangement dynamics that accompany the photodetachment of the aqueous tryptophan anion by intense, ∼5-fs laser pulses. The observed vibrational wave packet dynamics, in conjunction with density functional theory calculations, identify the vibrational modes of the tryptophan radical, which participate in structural rearrangement upon photodetachment. Aside from intramolecular vibrational modes, our results also point to the involvement of intermolecular modes that drive solvent reorganization about the N-H moiety of the indole sidechain. Our study offers new insight into the ultrafast molecular dynamics of ionized biomolecules and suggests that the present experimental approach can be extended to investigate the photoionization-or photodetachment-induced structural dynamics of larger biomolecules.

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Charge transfer reactions from tryptophan and tyrosine to sulfur-centered dimer radical cation in aqueous -sulfuric acid medium: a pulse radiolysis study

Cited by 8 publications

References 30 publications

Surface Stability and Morphology of Calcium Phosphate Tuned by pH Values and Lactic Acid Additives: Theoretical and Experimental Study

Surface Stability and Morphology of Calcium Phosphate Tuned by pH Values and Lactic Acid Additives: Theoretical and Experimental Study

Tuning Coordination Modes and Nucleation of Calcium Phosphate with Oligomeric Lactic Acid and pH Values: Theoretical and Experimental Study

Observation of intra- and intermolecular vibrational coherences of the aqueous tryptophan radical induced by photodetachment

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