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Zheng X, Yang N, Hou Y, Cai K. Dissecting amide-I vibrations in histidine dipeptide. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 292:122424. [PMID: 36750008 DOI: 10.1016/j.saa.2023.122424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 01/27/2023] [Accepted: 01/28/2023] [Indexed: 06/18/2023]
Abstract
The amide-I vibrational characteristics and conformational preferences of the model compound - histidine dipeptide (Ac-His-NHCH3, HISD) in gas phase and solution have been revealed with the help of ab initio calculations and wavefunction analyses. The Gibbs free energy surfaces (FESs) of solvated HISD were smoothed by solvent effect to exhibit different structural populations concerning various external environments. It was shown that the most stable conformations of HISD in CHCl3 and gas phase are C7eq, while those in DMSO and water are β and PPII, respectively. Compared with ALAD, the number of accessible conformational states on these FESs was predicted to be reduced due to the steric effect of imidazole group. The two amide-I normal modes of HISD were found to have intrinsically secondary structural dependencies, and be sensitive to surrounding environments. The average amide-Ia frequencies of HISD isomers in these environments were predicted to be almost the same as those of ALAD, while the amide-Ib mean frequencies were estimated to be lower than ALAD due to the intramolecular interactions between the imidazole group and amino-terminal amide unit. The good linear correlations between amide-I frequencies and the atomic electrostatic potentials (ESPs) of amide groups were also found to interpret the solvent-induced amide-I frequency shifts of HISD at the electronic structure level. These results allow us to gain a deep understanding of amide-I vibrations of HISD, and would be helpful for the site-specific conformational monitoring and spectral interpretation of solvated polypeptides.
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Affiliation(s)
- Xuan Zheng
- College of Chemistry, Chemical Engineering and Environment, Fujian Province Key Laboratory of Modern Analytical Science and Separation Technology, Fujian Provincial Key Laboratory of Pollution Monitoring and Control, Minnan Normal University, Zhangzhou 363000, PR China.
| | - Nairong Yang
- College of Chemistry, Chemical Engineering and Environment, Fujian Province Key Laboratory of Modern Analytical Science and Separation Technology, Fujian Provincial Key Laboratory of Pollution Monitoring and Control, Minnan Normal University, Zhangzhou 363000, PR China
| | - Yanjun Hou
- College of Chemistry, Chemical Engineering and Environment, Fujian Province Key Laboratory of Modern Analytical Science and Separation Technology, Fujian Provincial Key Laboratory of Pollution Monitoring and Control, Minnan Normal University, Zhangzhou 363000, PR China
| | - Kaicong Cai
- College of Chemistry and Materials Science, Fujian Provincial Key Laboratory of Advanced Materials Oriented Chemical Engineering, Fujian Normal University, Fuzhou 350007, PR China; Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Xiamen 361005, PR China; Fujian Provincial Key Laboratory of Featured Biochemical and Chemical Materials, Ningde Normal University, Ningde 352100, PR China.
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Hwang D, Schlenker CW. Photochemistry of carbon nitrides and heptazine derivatives. Chem Commun (Camb) 2021; 57:9330-9353. [PMID: 34528956 DOI: 10.1039/d1cc02745j] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We explore the photochemistry of polymeric carbon nitride (C3N4), an archetypal organic photocatalyst, and derivatives of its structural monomer unit, heptazine (Hz). Through spectroscopic studies and computational analysis, we have observed that Hz derivatives can engage in non-innocent hydrogen bonding interactions with hydroxylic species. The photochemistry of these complexes is influenced by intermolecular nπ*/ππ* mixing of non-bonding orbitals of each component and the relative energy of intermolecular charge-transfer (CT) states. Coupling of the former to the latter appears to facilitate proton-coupled electron transfer (PCET), resulting in biradical products. We have also observed that Hz derivatives exhibit an extremely rare inverted singlet/triplet energy splitting (ΔEST). In violation of Hund's multiplicity rules, the lowest energy singlet (S1) is stabilized relative to the lowest triplet (T1) electronic excited state. Exploiting this unique inverted ΔEST character has obvious implications for transformational discoveries in solid-state OLED lighting and photovoltaics. Harnessing this inverted ΔEST, paired with light-driven intermolecular PCET reactions, may enable molecular transformations relevant for applications ranging from solar energy storage to new classes of non-triplet photoredox catalysts for pharmaceutical development. To this end, we have explored the possibility of optically controlling the photochemistry of Hz derivatives using ultrafast pump-push-probe spectroscopy. In this case, the excited state branching ratios among locally excited states of the chromophore and the reactive intermolecular CT state can be manipulated with an appropriate secondary "push" excitation pulse. These results indicate that we can predictively redirect chemical reactivity with light in this system, which is an avidly sought achievement in the field of photochemistry. Looking forward, we anticipate future opportunities for controlling heptazine photochemistry, including manipulating PCET reactivity with a diverse array of substrates and optically delivering reducing equivalents with, for example, water as a partial source of electrons and protons. Furthermore, we wholly expect that, over the next decade, materials such as Hz derivatives, that exhibit inverted ΔEST character, will spawn a significant new research effort in the field of thin-film optoelectronics, where controlling recombination via triplet excitonic states can play a critical role in determining device performance.
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Affiliation(s)
- Doyk Hwang
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
| | - Cody W Schlenker
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.,Molecular Engineering & Sciences Institute, University of Washington, Seattle, Washington 98195-1652, USA.,Clean Energy Institute, University of Washington, Seattle, Washington 98195-1653, USA.
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Dong X, Wang S, Yu P, Yang F, Zhao J, Wu LZ, Tung CH, Wang J. Ultrafast Vibrational Energy Transfer through the Covalent Bond and Intra- and Intermolecular Hydrogen Bonds in a Supramolecular Dimer by Two-Dimensional Infrared Spectroscopy. J Phys Chem B 2020; 124:544-555. [PMID: 31873023 DOI: 10.1021/acs.jpcb.9b10431] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this work, the structural fluctuations and vibrational energy transfer dynamics in a supramolecular homodimer model, which is composed of 2-(9-anthracene)ureido-6-(1-undecyl)-4[1H]-pyrimidinone (UPAn) with quadruple intermolecular and single intramolecular hydrogen bonds (HBs), have been examined using ultrafast two-dimensional infrared (2D IR) and steady-state IR spectroscopies. A less structurally fluctuating intermolecular HB is found between the pyrimidinone C═O and ureido N-H groups. However, a larger structurally fluctuating intramolecular HB is suggested by the equilibrium and dynamical line-shape measurements of the ureido C═O stretch. Further, dynamical time-dependent 2D IR diagonal and off-diagonal signals show that intra- and intermolecular vibrational energy transfer processes occur on the picosecond timescale, where the latter is more efficient due to intermolecular hydrogen bonding interaction and through-space interaction.
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Affiliation(s)
- Xueqian Dong
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences , Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190 , P. R. China.,University of Chinese Academy of Sciences , Beijing 100049 , P. R. China
| | - Sumin Wang
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials , Technical Institute of Physics and Chemistry, Chinese Academy of Sciences , Beijing 100190 , P. R. China.,School of Materials and Chemical Engineering , Xi'an Technological University , Xi'an 710021 , P. R. China
| | - Pengyun Yu
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences , Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190 , P. R. China.,University of Chinese Academy of Sciences , Beijing 100049 , P. R. China
| | - Fan Yang
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences , Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190 , P. R. China
| | - Juan Zhao
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences , Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190 , P. R. China.,University of Chinese Academy of Sciences , Beijing 100049 , P. R. China
| | - Li-Zhu Wu
- University of Chinese Academy of Sciences , Beijing 100049 , P. R. China.,Key Laboratory of Photochemical Conversion and Optoelectronic Materials , Technical Institute of Physics and Chemistry, Chinese Academy of Sciences , Beijing 100190 , P. R. China
| | - Chen-Ho Tung
- University of Chinese Academy of Sciences , Beijing 100049 , P. R. China.,Key Laboratory of Photochemical Conversion and Optoelectronic Materials , Technical Institute of Physics and Chemistry, Chinese Academy of Sciences , Beijing 100190 , P. R. China
| | - Jianping Wang
- Beijing National Laboratory for Molecular Sciences, CAS Research/Education Center for Excellence in Molecular Sciences , Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190 , P. R. China.,University of Chinese Academy of Sciences , Beijing 100049 , P. R. China
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Zhang J. Two-dimensional infrared spectral explorations into bilayer and monolayer self-assemblies of amphiphilic polypeptides. J Biomol Struct Dyn 2020; 39:9-19. [PMID: 31914853 DOI: 10.1080/07391102.2020.1713891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Poly(2-(3-((2-hydroxyethyl)amino)-3-oxopropyl)ethyleneamido) (PHAOE) is an amphiphilic polypeptide. The self-assembly is significant, but the ultrafast dynamic analyses of the peptide self-assembly are exiguous and worth further exploring. In this investigation, the temporal dynamic characteristics of the aggregates and unaggregated PHAOEs are mined by the two-dimensional infrared (2D IR) spectroscopy. The homogeneous and inhomogeneous diffusion processes of the carbonyl stretching modes of the unaggregated PHAOEs are slower than those of the self-assemblies. The inhomogeneous spectral diffusion proportion of the biopolymer PHAOE in methanol is greater than that in dimethyl sulfoxide (DMSO). The solvation shells surround the aggregates and unaggregated PHAOEs in the protic solvent methanol, but there are not any solvation shells around the aggregates or unaggregated PHAOEs in the dipolar solvent DMSO. The massive hydrogen-bonded monolayer self-assembly has merely an aggregate of PHAOEs and no solvation shell in DMSO. But the hydrogen-bonded bilayer self-assembly has a self-assembled methanol shell and an interior aggregate of PHAOEs in methanol. The self-assemblies of PHAOEs motivate the methanols to self-assemble. The large delocalized amide structure results in the fast spectral diffusion of the carbonyl stretching mode.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Jun Zhang
- Beijing National Laboratory for Molecular Sciences, Molecular Reaction Dynamics Laboratory, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry Chinese Academy of Sciences, Beijing, P. R. China.,University of Chinese Academy of Sciences, Beijing, P. R. China
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