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Campomizzi CS, Uttamrao PP, Stallone JJ, Rathinavelan T, Estrada DF. Asparagine-85 Stabilizes a Structural Active Site Water Network in CYP121A1 of Mycobacterium tuberculosis. Biochemistry 2024; 63:711-722. [PMID: 38380587 DOI: 10.1021/acs.biochem.3c00555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
The cytochrome P450 enzyme CYP121A1 endogenously catalyzes the formation of a carbon-carbon bond between the two phenol groups of dicyclotyrosine (cYY) in Mycobacterium tuberculosis (Mtb). One of 20 CYP enzymes in Mtb, CYP121A1 continues to garner significant interest as a potential drug target. The accompanying reports the use of 19F NMR spectroscopy, reconstituted activity assays, and molecular dynamics simulations to investigate the significance of hydrogen bonding interactions that were theorized to stabilize a static active site water network. The active site residue Asn-85, whose hydrogen bonds with the diketopiperazine ring of cYY contributes to a contiguous active site water network in the absence of cYY, was mutated to a serine (N85S) and to a glutamine (N85Q). These conservative changes in the hydrogen bond donor side chain result in inactivation of the enzyme. Moreover, the N85S mutation induces reverse type-I binding as measured by absorbance difference spectra. NMR spectra monitoring the ligand-adaptive FG-loop and the active site Trp-182 side chain confirm that disruption of the active site water network also significantly alters the structure of the active site. These data were consistent with dynamics simulations of N85S and N85Q that demonstrate that a compromised water network is responsible for remodeling of the active site B-helix and a repositioning of cYY toward the heme. These findings implicate a slowly exchanging water network as a critical factor in CYP121A1 function and a likely contributor to the unusual rigidity of the structure.
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Affiliation(s)
- Christopher S Campomizzi
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Science, University at Buffalo, Buffalo, New York 14203, United States
| | - Patil Pranita Uttamrao
- Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502284, India
| | - Jack J Stallone
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Science, University at Buffalo, Buffalo, New York 14203, United States
| | - Thenmalarchelvi Rathinavelan
- Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, Telangana 502284, India
| | - D Fernando Estrada
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Science, University at Buffalo, Buffalo, New York 14203, United States
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2
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Grieco A, Ruiz-Fresneda MA, Gómez-Mulas A, Pacheco-García JL, Quereda-Moraleda I, Pey AL, Martin-Garcia JM. Structural dynamics at the active site of the cancer-associated flavoenzyme NQO1 probed by chemical modification with PMSF. FEBS Lett 2023; 597:2687-2698. [PMID: 37726177 DOI: 10.1002/1873-3468.14738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 08/02/2023] [Accepted: 08/29/2023] [Indexed: 09/21/2023]
Abstract
A large conformational heterogeneity of human NAD(P)H:quinone oxidoreductase 1 (NQO1), a flavoprotein associated with various human diseases, has been observed to occur in the catalytic site of the enzyme. Here, we report the X-ray structure of NQO1 with phenylmethylsulfonyl fluoride (PMSF) at 1.6 Å resolution. Activity assays confirmed that, despite being covalently bound to the Tyr128 residue at the catalytic site, PMSF did not abolish NQO1 activity. This may indicate that the PMSF molecule does not reduce the high flexibility of Tyr128, thus allowing NADH and DCPIP substrates to bind to the enzyme. Our results show that targeting Tyr128, a key residue in NQO1 function, with small covalently bound molecules could possibly not be a good drug discovery strategy to inhibit this enzyme.
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Affiliation(s)
- Alice Grieco
- Department of Crystallography & Structural Biology, Institute of Physical Chemistry Blas Cabrera, Spanish National Research Council (CSIC), Madrid, Spain
| | | | | | | | - Isabel Quereda-Moraleda
- Department of Crystallography & Structural Biology, Institute of Physical Chemistry Blas Cabrera, Spanish National Research Council (CSIC), Madrid, Spain
| | - Angel L Pey
- Department of Physical Chemistry, University of Granada, Granada, Spain
- Department of Physical Chemistry, Unit of Excellence in Applied Chemistry to Biomedicine and Environment, and Institute of Biotechnology, University of Granada, Granada, Spain
| | - Jose M Martin-Garcia
- Department of Crystallography & Structural Biology, Institute of Physical Chemistry Blas Cabrera, Spanish National Research Council (CSIC), Madrid, Spain
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3
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Duan L, Tang B, Luo S, Xiong D, Wang Q, Xu X, Zhang JZH. Entropy driven cooperativity effect in multi-site drug optimization targeting SARS-CoV-2 papain-like protease. Cell Mol Life Sci 2023; 80:313. [PMID: 37796323 PMCID: PMC11072831 DOI: 10.1007/s00018-023-04985-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 09/07/2023] [Accepted: 09/26/2023] [Indexed: 10/06/2023]
Abstract
Papain-like protease (PLpro), a non-structural protein encoded by SARS-CoV-2, is an important therapeutic target. Regions 1 and 5 of an existing drug, GRL0617, can be optimized to produce cooperativity with PLpro binding, resulting in stronger binding affinity. This work investigated the origin of the cooperativity using molecular dynamics simulations combined with the interaction entropy (IE) method. The regions' improvement exhibits cooperativity by calculating the binding free energies between the complex of PLpro-inhibitor. The thermodynamic integration method further verified the cooperativity generated in the drug improvement. To further determine the specific source of cooperativity, enthalpy and entropy in the complexes were calculated using molecular mechanics/generalized Born surface area and IE. The results show that the entropic change is an important contributor to the cooperativity. Our study also identified residues P248, Q269, and T301 that play a significant role in cooperativity. The optimization of the inhibitor stabilizes these residues and minimizes the entropic loss, and the cooperativity observed in the binding free energy can be attributed to the change in the entropic contribution of these residues. Based on our research, the application of cooperativity can facilitate drug optimization, and provide theoretical ideas for drug development that leverage cooperativity by reducing the contribution of entropy through multi-locus binding.
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Affiliation(s)
- Lili Duan
- School of Physics and Electronics, Shandong Normal University, Jinan, 250014, China.
| | - Bolin Tang
- School of Physics and Electronics, Shandong Normal University, Jinan, 250014, China
| | - Song Luo
- School of Physics and Electronics, Shandong Normal University, Jinan, 250014, China
| | - Danyang Xiong
- School of Physics and Electronics, Shandong Normal University, Jinan, 250014, China
| | - Qihang Wang
- School of Physics and Electronics, Shandong Normal University, Jinan, 250014, China
| | - Xiaole Xu
- School of Physics and Electronics, Shandong Normal University, Jinan, 250014, China
| | - John Z H Zhang
- Faculty of Synthetic Biology and Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, 200062, China.
- NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai, 200062, China.
- Department of Chemistry, New York University, New York, NY, 10003, USA.
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4
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Pal S, Roy R, Paul S. Deciphering the Role of ATP on PHF6 Aggregation. J Phys Chem B 2022; 126:4761-4775. [PMID: 35759245 DOI: 10.1021/acs.jpcb.2c01768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The aggregation of Tau protein, which are involved in Alzheimer's disease, are associated with the self-assembly of the hexapeptide sequence, paired helical filament 6 (PHF6) from repeat 3 of Tau. In order to treat Alzheimer's disease and other such tauopathies, one of the therapeutic strategies is to inhibit aggregation of Tau and its nucleating segments. Therefore, we have studied the effect of adenosine triphosphate (ATP) on the aggregation of PHF6. ATP has, interestingly, demonstrated its ability to inhibit and dissolve protein aggregates. Using classical molecular dynamics simulations, we observed that the hydrophobic core of PHF6 segment displays extended β-sheet conformation, which stabilizes PHF6 aggregates. However, the distribution of ATP around the vicinity of the peptides enables PHF6 to remain discrete and attain random coil conformers. The interpeptide interactions are substituted by PHF6-ATP interactions through hydrogen bonding and hydrophobic interactions (including π-π stacking). Furthermore, the adenosine moiety of ATP contributes more than the triphosphate chain toward PHF6-ATP interaction. Ultimately, this work establishes the inhibitory activity of ATP against Tau aggregation; hence, the therapeutic effect of ATP should be explored further in regard to the effective treatment of Alzheimer's disease.
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Affiliation(s)
- Saikat Pal
- Department of Chemistry, Indian Institute of Technology, Guwahati, Assam 781039, India
| | - Rituparna Roy
- Department of Chemistry, Indian Institute of Technology, Guwahati, Assam 781039, India
| | - Sandip Paul
- Department of Chemistry, Indian Institute of Technology, Guwahati, Assam 781039, India
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6
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Dynamic equilibria in protein kinases. Curr Opin Struct Biol 2021; 71:215-222. [PMID: 34425481 DOI: 10.1016/j.sbi.2021.07.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 06/15/2021] [Accepted: 07/14/2021] [Indexed: 12/14/2022]
Abstract
Structural changes involved in protein kinase activation and ligand binding have been determined from a wealth of X-ray crystallographic evidence. Recent solution studies using NMR, EPR, HX-MS, and fluorescence techniques have deepened this understanding by highlighting the underlying energetics and dynamics of multistate conformational ensembles. This new research is showing how activation mechanisms and ligand binding alter the internal motions of kinases and enable allosteric coupling between distal regulatory regions and the active site.
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Akella R, Humphreys JM, Sekulski K, He H, Durbacz M, Chakravarthy S, Liwocha J, Mohammed ZJ, Brautigam CA, Goldsmith EJ. Osmosensing by WNK Kinases. Mol Biol Cell 2021; 32:1614-1623. [PMID: 33689398 PMCID: PMC8684725 DOI: 10.1091/mbc.e20-01-0089] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 02/11/2021] [Accepted: 02/22/2021] [Indexed: 12/13/2022] Open
Abstract
With No Lysine (K) WNK kinases regulate electro-neutral cotransporters that are controlled by osmotic stress and chloride. We showed previously that autophosphorylation of WNK1 is inhibited by chloride, raising the possibility that WNKs are activated by osmotic stress. Here we demonstrate that unphosphorylated WNK isoforms 3 and 1 autophosphorylate in response to osmotic pressure in vitro, applied with the crowding agent polyethylene glycol (PEG)400 or osmolyte ethylene glycol (EG), and that this activation is opposed by chloride. Small angle x-ray scattering of WNK3 in the presence and absence of PEG400, static light scattering in EG, and crystallography of WNK1 were used to understand the mechanism. Osmosensing in WNK3 and WNK1 appears to occur through a conformational equilibrium between an inactive, unphosphorylated, chloride-binding dimer and an autophosphorylation-competent monomer. An improved structure of the inactive kinase domain of WNK1, and a comparison with the structure of a monophosphorylated form of WNK1, suggests that large cavities, greater hydration, and specific bound water may participate in the osmosensing mechanism. Our prior work showed that osmolytes have effects on the structure of phosphorylated WNK1, suggestive of multiple stages of osmotic regulation in WNKs.
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Affiliation(s)
- Radha Akella
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - John M. Humphreys
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Kamil Sekulski
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Haixia He
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Mateusz Durbacz
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Srinivas Chakravarthy
- Department of Biology, Chemistry, & Physical Sciences, APS/Illinois Institute of Technology, Argonne, IL 60439
| | - Joanna Liwocha
- Department of Molecular Biology, The University of Texas Southwestern Medical Center, Dallas, TX 75390
| | | | - Chad A. Brautigam
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390
- Department of Microbiology, The University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Elizabeth J. Goldsmith
- Department of Biophysics, The University of Texas Southwestern Medical Center, Dallas, TX 75390
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Yang SL, Li G, Guo MY, Liu WS, Bu R, Gao EQ. Positive Cooperative Protonation of a Metal-Organic Framework: pH-Responsive Fluorescence and Proton Conduction. J Am Chem Soc 2021; 143:8838-8848. [PMID: 34076423 DOI: 10.1021/jacs.1c03432] [Citation(s) in RCA: 73] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Positive cooperative binding, a phenomenon prevalent in biological processes, holds great appeal for the design of highly sensitive responsive molecules and materials. It has been demonstrated that metal-organic frameworks (MOFs) can show positive cooperative adsorption to the benefit of gas separation, but potential binding cooperativity is largely ignored in the study of sensory MOFs. Here, we report the first demonstration of positive cooperative protonation of a MOF and the relevant pH response in fluorescence and proton conduction. The MOF is built of Zr-O clusters and bipyridyl-based tetracarboxylate linkers and has excellent hydrolytic stability. It shows a unique pH response that features two synchronous abrupt turn-off and turn-on fluorescent transitions. The abrupt transitions, which afford high sensitivity to small pH fluctuations, are due to cooperative protonation of the pyridyl sites with a Hill coefficient of 1.6. The synchronous dual-emission response, which leads to visual color change, is ascribable to proton-triggered switching between (n, π*) and (π, π*) emissions. The latter emission can be quenched by electron donating anion-dependent through photoinduced electron transfer and ground-state charge transfer. Associated with cooperative protonation, the proton conductivity of the MOF is abruptly enhanced at low pH by two orders, but overhigh acid concentration is adverse because excessive anions can interrupt the conducting networks. Our work shows new perspectives of binding cooperativity in MOFs and should shed new light on the development of responsive fluorescent MOFs and proton conductive materials.
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Affiliation(s)
- Shuai-Liang Yang
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Gen Li
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Meng-Yue Guo
- Engineering Research Centre for Nanophotonics and Advanced Instrument, School of Physics and Electronic Science, East China Normal University, Shanghai 200062, China
| | - Wan-Shan Liu
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Ran Bu
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - En-Qing Gao
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
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9
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Roy R, Paul S. Potential of ATP toward Prevention of hIAPP Oligomerization and Destabilization of hIAPP Protofibrils: An In Silico Perspective. J Phys Chem B 2021; 125:3510-3526. [PMID: 33792323 DOI: 10.1021/acs.jpcb.1c00313] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The aggregation of an intrinsically disordered protein, human islet amyloid polypeptide (hIAPP), leads to one of the most prevalent endocrine disorders, type II diabetes mellitus (T2DM). Hence inhibition of hIAPP aggregation provides a possible therapeutic approach for the treatment of T2DM. In this regard, a new aspect of adenosine triphosphate (ATP), which is widely known as the energy source for biological reactions, has recently been discovered, where it can inhibit the formation of protein aggregates and simultaneously dissolve preformed aggregates at a millimolar concentration scale. In this work, we investigate the effect of ATP on the aggregation of an amyloidogenic segment of hIAPP, hIAPP22-28, and also of the full length sequence. Using all-atom classical molecular dynamics simulations, we observe that the tendency of hIAPP to oligomerize into β-sheet conformers is inhibited by ATP, due to which the peptides remain distant, loosely packed random monomers. Moreover, it can also disassemble preformed hIAPP protofibrils. ATP preferentially interacts with the hydrophobic residues of hIAPP22-28 fragment and the terminal and turn residues of the full length peptide. The hydrogen bonding, hydrophobic, π-π, and N-H-π stacking interactions are the driving forces for the ATP induced inhibition of hIAPP aggregation. Interestingly, the hydrophobic adenosine of ATP is found to be more in contact with the peptide residues than the hydrophilic triphosphate moiety. The insight into the inhibitory mechanism of ATP on hIAPP aggregation can prove to be beneficial for the design of novel amyloid inhibitors in the future.
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Affiliation(s)
- Rituparna Roy
- Department of Chemistry, Indian Institute of Technology, Guwahati, Assam, India 781039
| | - Sandip Paul
- Department of Chemistry, Indian Institute of Technology, Guwahati, Assam, India 781039
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10
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Setny P. Conserved internal hydration motifs in protein kinases. Proteins 2020; 88:1578-1591. [DOI: 10.1002/prot.25977] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 05/18/2020] [Accepted: 07/05/2020] [Indexed: 01/14/2023]
Affiliation(s)
- Piotr Setny
- Centre of New Technologies University of Warsaw Warsaw Poland
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11
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Leitner DM, Hyeon C, Reid KM. Water-mediated biomolecular dynamics and allostery. J Chem Phys 2020; 152:240901. [DOI: 10.1063/5.0011392] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Affiliation(s)
- David M. Leitner
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, USA
| | - Changbong Hyeon
- Korea Institute for Advanced Study, Seoul 02455, South Korea
| | - Korey M. Reid
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, USA
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12
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Abstract
The oligomerization of Aβ16-22 peptide, which is the hydrophobic core region of full-length Aβ1-42, causes Alzheimer's disease (AD). This progressive neurodegenerative disease affects over 44 million people worldwide. However, very few synthesized drug molecules are available to inhibit the aggregation of Aβ. Recently, experimental studies have shown that the biological ATP molecule prevents Aβ fibrillation at the millimolar scale; however, the significance of ATP molecules on Aβ fibrillation and the mechanism behind it remain elusive. We have carried out a total of 7.5 μs extensive all-atom molecular dynamics and 8.82 μs of umbrella sampling in explicit water using AMBER14SB, AMBER99SB-ILDN, and AMBER-FB15 force fields for Aβ16-22 peptide, to investigate the role of ATP on the disruption of Aβ16-22 prefibrils. From various analyses, such as secondary structure analysis, residue-wise contact map, SASA, and interaction energies, we have observed that, in the presence of ATP, the aggregation of Aβ16-22 peptide is very unfavorable. Moreover, the biological molecule ATP interacts with the Aβ16-22 peptide via hydrogen bonding, π-π stacking, and NH-π interactions which, ultimately, prevent the aggregation of Aβ16-22 peptide. Hence, we assume that the deficiency of ATP may cause Alzheimer's disease (AD).
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Affiliation(s)
- Saikat Pal
- Department of Chemistry , Indian Institute of Technology , Guwahati , Assam 781039 , India
| | - Sandip Paul
- Department of Chemistry , Indian Institute of Technology , Guwahati , Assam 781039 , India
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Jing B, Ferreira M, Gao Y, Wood C, Li R, Fukuto M, Liu T, Zhu Y. Unconventional Complex Coacervation between Neutral Polymer and Inorganic Polyoxometalate in Aqueous Solution via Direct Water Mediation. Macromolecules 2019. [DOI: 10.1021/acs.macromol.9b01091] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Benxin Jing
- Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, United States
| | - Manuela Ferreira
- Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, United States
| | - Yunyi Gao
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
| | - Christopher Wood
- Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, United States
| | - Ruipeng Li
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Masafumi Fukuto
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Tianbo Liu
- Department of Polymer Science, The University of Akron, Akron, Ohio 44325, United States
| | - Yingxi Zhu
- Department of Chemical Engineering and Materials Science, Wayne State University, Detroit, Michigan 48202, United States
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Kundu A, Verma PK, Cho M. Water Structure and Dynamics in the Stern Layer of Micelles: Femtosecond Mid-Infrared Pump-Probe Spectroscopy Study. J Phys Chem B 2019; 123:5238-5245. [PMID: 31145621 DOI: 10.1021/acs.jpcb.9b03183] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular-level understanding of the water structure and dynamics in the Stern layer of micelles is important to elucidate the active role of water in biological processes on membrane surfaces. Micelles and reverse micelles are considered to be excellent membrane model systems. Here, to address the question of whether or not the spatial confinement effect on water in reverse micelles and nanometric water pool systems plays a role in modulating water dynamics, we consider four different aqueous micelle solutions and study the water dynamics in the Stern layer of micelles using a femtosecond mid-infrared pump-probe spectroscopy technique. Vibrational energy relaxation and rotational dynamics of the O?D stretch mode of HDO and the azido stretch mode of hydrazoic acid are critically dependent on the charge, polarity, and chemical structure of the surfactant head group. In particular, water molecules in the Stern layer of micelles, which are not in spatially confined environments, are notably different from those in bulk water. This finding clearly indicates that changes in the vibrational and rotational dynamics of water molecules, even in spatially confined systems, are mainly induced by surface effects instead of spatial confinement effects. We believe that the present experimental results are of importance for understanding water-involved biochemical processes on biological membranes.
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Affiliation(s)
- Achintya Kundu
- Center for Molecular Spectroscopy and Dynamics , Institute for Basic Science (IBS) , Seoul 02841 , Republic of Korea.,Department of Chemistry , Korea University , Seoul 02841 , Republic of Korea
| | - Pramod Kumar Verma
- Center for Molecular Spectroscopy and Dynamics , Institute for Basic Science (IBS) , Seoul 02841 , Republic of Korea.,Department of Chemistry , Korea University , Seoul 02841 , Republic of Korea
| | - Minhaeng Cho
- Center for Molecular Spectroscopy and Dynamics , Institute for Basic Science (IBS) , Seoul 02841 , Republic of Korea.,Department of Chemistry , Korea University , Seoul 02841 , Republic of Korea
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