Salting-out of methane in the aqueous solutions of urea and sarcosine

Dixit, Manasvi; Chatterjee, Anupam; Tembe, B. L.

doi:10.1007/s12039-016-1052-x

Cited by 6 publications

(5 citation statements)

References 66 publications

(52 reference statements)

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“…The potentials of mean force (PMFs) are widely utilized to investigate the stability of clusters, as demonstrated in various studies. ,,− Accordingly, in this study, we have computed the PMFs between the terminal groups and also between the dipeptide and the terminal groups, employing the following equation W ( r ) = prefix− k B T .25em log ( g false( r false) ) where k B represents the Boltzmann constant in kJ mol –1 /K, T is the temperature of the system, and g ( r ) denotes the RDF between the terminal groups. Figure illustrates the PMFs between the two terminal groups as a function of their distance.…”

Section: Resultsmentioning

confidence: 99%

Effect of Impurities on the Formation of End-Group Clusters in Natural Rubber: Phenylalanine Dipeptide as an Impurity Protein

Dixit,

Taniguchi

2024

Macromolecules

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Natural rubber (NR), containing nonrubber constituents such as proteins, exhibits exceptional characteristics including high toughness, tear resistance, and wet skid resistance. Gaining a thorough understanding of the interplay between proteins and the terminal groups of the cis-1,4-polyisoprene chains in NR is vital for comprehending the superior properties of NR in comparison to synthetic polyisoprene rubber. The terminal ends of the cis-1,4-polyisoprene chains in NR encompass two distinct types of terminal groups: ω terminals and α terminals. Extensive investigations employing solid-state NMR analysis have revealed the structures of the ω and α terminals in NR, identifying ω as dimethyl allyl-(trans-1,4-isoprene) 2 (DMA), while the α terminals have been categorized into six types [Oouchi, M.; Ukawa, J.; Ishii, Y.; Maeda, H. Structural analysis of the terminal groups in Commercial Hevea Natural Rubber by 2D-NMR with DOSY filters and multiple-WET methods using ultrahigh-field NMR. Biomacromolecules 2019Biomacromolecules , 20, 1394Biomacromolecules −1400. In this study, our primary focus is to explore the interaction between phenylalanine dipeptide (PAP) and the terminal groups within six types of melt systems ( ω PI αn + P, n = 1•••6, "P" stands for PAP). By utilizing equilibrated systems, various physical quantities were estimated, including end-to-end distance (R ee ), radius of gyration (R g ), end-to-end vector autocorrelation function (C(t)), average rotational relaxation time τ rot , self-diffusion coefficients of polymer chains, radial distribution functions (RDFs) of terminal groups around PAP, and the survival probability P(τ) for terminal groups surrounding PAP. Analysis of C(t) and τ rot unveiled that PAP significantly hinders the dynamics of hydroxy-terminated and ester-terminated polyisoprene chains in the ω PI α1-to-α6 melt systems. Examination of RDFs demonstrated a robust association between PAP molecules and α terminals compared to ω terminal groups. Moreover, the local density of α terminal groups around other α terminal groups was notably reduced in the presence of PAP. The association between PAP and DMA was found to be weaker than that of DMA and DMA, indicating a weak correlation between PAP molecules and ω terminal groups. By employing the potentials of mean force, we conducted an investigation to calculate the cluster formation fraction of terminal groups associated with PAP as well as terminal groups forming clusters of various sizes in the 13 melt systems. Our findings revealed that in the H PI H , ω PI α1 , ω PI α3 , and ω PI α5 systems, firm cluster formation was not observed without PAP. However, in the presence of PAP, stable clusters comprising PAP − α1, PAP − α3, and PAP − α5 were formed. Conversely, in the ω PI α2 + P, ω PI α4 + P, and ω PI α6 + P systems, stable clusters involving α2 and α2, PAP and α2, α4 and α4, PAP and α4, α6 and α6, and PAP and α6 with sizes ranging from 2 to 9 were observed. These findings provide evidence for the formation of physical junction points (PJ...

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Section: Resultsmentioning

confidence: 99%

Effect of Impurities on the Formation of End-Group Clusters in Natural Rubber: Phenylalanine Dipeptide as an Impurity Protein

Dixit,

Taniguchi

2024

Macromolecules

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“…Although the encountering of end groups can be observed with a certain fraction, it is not sufficient to determine if the encountered end groups form a stable physical junction or cluster. To assess the stability of clusters, potentials of mean force (PMFs) are commonly employed. ,,− Hence, we performed calculations of the PMFs between the terminal groups employing the following equation W ( r ) = prefix− k normalB T log ( g false( r false) ) where k B denotes the Boltzmann constant in kJ mol –1 /K, T represents the system’s temperature, and g ( r ) corresponds to the RDF between the terminal groups. Figure illustrates the PMFs between the two terminal groups, displayed as a function of the distance.…”

Section: Resultsmentioning

confidence: 99%

Role of Terminal Groups of cis-1,4-Polyisoprene Chains in the Formation of Physical Junction Points in Natural Rubber

Dixit

Taniguchi

2023

Biomacromolecules

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The terminal structures of cis-1,4-polyisoprene (PI) chains play a vital role in the excellent comprehensive performance of Hevea natural rubber (NR) with properties such as high toughness, tear-resistance, and wet skid resistance. The cis-1,4polyisoprene chain constituting NR exhibits a distinct composition of terminal groups comprising two distinct types, namely, the ω and α terminal groups. The structures of the ω terminal [dimethyl allyl (DMA)-(trans-1,4-isoprene) 2 ] and six kinds of α end groups of the polymer chain of NR have been explored by utilizing a newly developed 2D NMR method. In the present work, we examine different kinds of PI melt systems, and we choose various combinations of terminal groups: Hydrogen, one DMA unit with two trans isoprene units as ω end groups and ester-terminated isopentene (α1), hydroxy-terminated isopentene (α2), ester-terminated isobutane (α3), hydroxy-terminated isobutane (α4), esterterminated 1,4-cis-isoprene (α5), and hydroxy-terminated 1,4-cis-isoprene (α6), i.e., H PI H (PI 0 )−pure PI (Hydrogen terminal), ω PI α1 (PI I ), ω PI α2 (PI II ), ω PI α3 (PI III ), ω PI α4 (PI IV ), ω PI α5 (PI V ), and ω PI α6 (PI VI ). We evaluated dynamic and static properties of PI chains such as the end-to-end vector autocorrelation function (C(t)), its average relaxation time (τ), end-to-end distance (R ee ), and radius of gyration (R g ). We also estimated the diffusion coefficients of polyisoprene chains and pair correlation functions [radial distribution functions (RDFs)], potentials of mean force (PMFs) in between end residues, and survival probability (P(τ)) of end groups around the end group by analyzing the equilibrated trajectories of full-atom MD simulations. As per the examination of C(t), rotational relaxation time τ, and RDFs, we discovered that the existence of a strong hydrogen bond in α2−α2, α4−α4, and α6−α6 residues makes the dynamics of hydroxy-terminated polyisoprene chains in ω PI α2,α4,α6 melt systems slower. From the analyses of RDFs and PMFs (W(r)), the association between [α2]−[α2], [α4]−[α4], and [α6]−[α6] terminals in ω PI α2,α4,α6 melt systems is significantly stronger than in [ISO]−[ISO] [Hydrogen terminated 1,4-cis-isoprene:(ISO)] in H PI H and ω−ω, [α1]−[α1], [α3]−[α3], and [α5]− [α5] in ω PI α1,α3,α5 systems. We quantified the fraction of cluster formation of terminal groups of a given size in the seven PI melt systems by employing the criteria of PMFs. It is revealed that no stable cluster exists in the H PI H , ω PI α1 , ω PI α3 , and ω PI α5 melt systems. Conversely, in the ω PI α2 , ω PI α4 , and ω PI α6 systems, we perceived stable clusters of [(α2) p ] [(α4) p ] and [(α6) p ] end groups where p (2 ≤ x ≤ 6). These stable clusters validate the presence of physical junction points in between hydroxy-terminated polyisoprene chains through their α2, α4, and α6 terminals. These physical junction points might be crucial for superior properties of NR such as high toughness, crack growth resistance, and strain-induced crystallization.

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“…The observation indicates that the end-groups encounter each other with a certain fraction; however, their stability as branch points or stable clusters remains undetermined. To address this, potentials of mean force (PMFs) have emerged as a widely used approach for assessing the stability of clusters in various research studies. ,,− In this study, we compute the PMFs between the terminal groups using the following equation W ( r ) = prefix− k B T .25em log ( g false( r false) ) where T is the temperature of the system, k B is the Boltzmann constant in kJ mol –1 /K, and g ( r ) represents the radial distribution function between the terminal groups. This equation allows us to derive the PMFs, which provide essential insights into the thermodynamic stability and interactions of the terminal groups in the system.…”

Section: Resultsmentioning

confidence: 99%

Exploring the Role of Hydroxy- and Phosphate-Terminated cis-1,4-Polyisoprene Chains in the Formation of Physical Junction Points in Natural Rubber: Insights from Molecular Dynamics Simulations

Dixit,

Taniguchi

2024

ACS Polym. Au

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This study elucidates the pivotal role of terminal structures in cis-1,4-polyisoprene (PI) chains, contributing to the exceptional mechanical properties of Hevea natural rubber (NR). NR's unique networking structure, crucial for crack resistance, elasticity, and strain-induced crystallization, involves two terminal groups, ω and α. The proposed ω terminal structure is dimethyl allyl-(trans-1,4-isoprene) 2 , and α terminals exist in various forms, including hydroxy, ester, and phosphate groups. Among others, we investigated three types of cis-1,4-PI with different terminal combinations: H PI H (pure PI with H terminal), ω PI α6 (PI with ω and α6 terminals), and ω PI POd 4 (PI with ω and PO 4 terminals) and revealed significant dynamics variations. Hydrogen bonds between α6 and α6 and PO 4 and PO 4 residues in ω PI α6 and ω PI POd 4 systems induce slower dynamics of hydroxy-and phosphate-terminated PI chains. Associations between α6 and α6 and PO 4 and PO 4 terminals are markedly stronger than ω and ω, and hydrogen terminals in H PI H and ω PI α6,POd 4 systems. Phosphate terminals exhibit a stronger mutual association than hydroxy terminals. Potentials of mean force analysis and cluster-formation-fraction computations reveal stable clusters in ω PI α6 and ω PI POd 4 , supporting the formation of polar aggregates (physical junction points). Notably, phosphate terminal groups facilitate large and highly stable phosphate polar aggregates, crucial for the natural networking structure responsible for NR's outstanding mechanical properties compared to synthetic PI rubber. This comprehensive investigation provides valuable insights into the role of terminal groups in cis-1,4-PI melt systems and their profound impact on the mechanical properties of NR.

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Salting-out of methane in the aqueous solutions of urea and sarcosine

Cited by 6 publications

References 66 publications

Effect of Impurities on the Formation of End-Group Clusters in Natural Rubber: Phenylalanine Dipeptide as an Impurity Protein

Effect of Impurities on the Formation of End-Group Clusters in Natural Rubber: Phenylalanine Dipeptide as an Impurity Protein

Role of Terminal Groups of cis-1,4-Polyisoprene Chains in the Formation of Physical Junction Points in Natural Rubber

Exploring the Role of Hydroxy- and Phosphate-Terminated cis-1,4-Polyisoprene Chains in the Formation of Physical Junction Points in Natural Rubber: Insights from Molecular Dynamics Simulations

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