Femtosecond infrared (IR) pump probe and dynamic hole burning experiments were used to examine the ultrafast response of modes in 1600−1700 cm-1 region (the so-called amide I modes) N-methylacetamide (NMA) three small globular peptides, apamin, scyllatoxin, bovine pancreatic trypsin inhibitor (BPTI). A value 16 was found for anharmonicity vibration. Vibrational relaxation all investigated peptides occurs ca. 1.2 ps. An even faster 450 fs is obtained NMA, a model peptide unit. The vibrational...

A form of two-dimensional (2D) vibrational spectroscopy, which uses two ultrafast IR laser pulses, is used to examine the structure a cyclic penta-peptide in solution. Spectrally resolved cross peaks occur off-diagonal region 2D spectrum amide I region, analogous those NMR spectroscopy. These measure coupling between different groups structure. Their intensities and polarizations relate directly three-dimensional peptide. With help model Hamiltonian, supplemented by density functional...

Using polarization sensitive two-dimensional (2D) vibrational spectroscopy on the amide I mode, central backbone structure of trialanine in aqueous solution is investigated. We exploit sensitivity 2D pump−probe signal to reveal cross-peak hidden under strong diagonal peaks. The dihedral angles φ and ψ characterizing peptide are derived directly from intensity anisotropy, demonstrating potential as a tool for elucidation.

The vibrational cooling of azobenzene after photoisomerization is investigated by time resolved IR spectroscopy with femtosecond resolution. Transient difference spectra were obtained in a frequency range where phenyl ring modes and the central N=N-stretching mode absorbs. experimental data are discussed terms simple theoretical model which was derived order to account for off-diagonal anharmonicity between high-frequency bath remaining low-frequency polyatomic molecule. It shown that these...

The first femtosecond three-pulse photon echo experiment of a vibrational transition is presented. A mode the azide ion ${\mathrm{N}}_{3}^{\ensuremath{-}}$ at $2043{\mathrm{cm}}^{\ensuremath{-}1}$ used to probe impulsively excited energy distribution and hence dynamics water around ion. frequency correlations decay on time scales about 80 fs 1.3 ps, while small part remains for longer than 10 ps. ps residence hydrogen bonds Major differences between optical echoes are addressed.

We report on an intense mid-infrared light source that provides femtosecond pulses a microjoule energy level, broadly tunable in the 3–20-µm wavelength range with pulse durations as short 50 fs at 5 µm. The are generated by phase-matched difference-frequency mixing GaSe of near-infrared signal and idler parametric device based 1-kHz Ti:sapphire amplifier system. Pulse characterized different techniques including autocorrelation measurements AgGaS2, two-photon absorption InSb,...

An experimental and theoretical study of intrinsic correlations noise-suppression mechanisms in two-stage femtosecond mid-IR light sources is presented. The setup, based on parametric amplification BBO subsequent difference-frequency mixing AgGaS2, delivers ≈100‐fs pulses with 1–2‐µJ energy. Exceptionally low pulse-energy fluctuations only 0.2% the λ≈3–6 µm are found, which much smaller than Ti:sapphire amplifer noise. noise suppression analyzed found to stem from interplay between...

We present the first infrared photon echo study of liquid water. For O-H stretch vibration HDO in ${\mathrm{D}}_{2}\mathrm{O}$, femtosecond four-wave mixing experiments reveal an extraordinary short pure dephasing time ${T}_{2}^{*}$ on order 90 fs. This unusually fast scale is rationalized by taking into account large anharmonicity hydrogen bonded stretching mode.

Nonlinear time-resolved vibrational spectroscopy is used to compare spectral broadening of the amide I band small peptide trialanine with that N-methylacetamide, a commonly model system for bond. In contrast significantly inhomogeneously broadened. Employing classical molecular-dynamics simulations combined density-functional-theory calculations, origin inhomogeneity investigated. While both systems exhibit similar hydrogen-bonding dynamics, it found conformational dynamics causes...

The vibrational relaxation time of the cyanide ion in H2O and D2O was measured by IR-pump–IR-probe experiments. isotopic composition varied order vary oscillation frequency CN− mode. In D2O, rate is accelerated from 120 to 71 ps when increasing 2004 cm−1 (13C15N) 2079 (12C14N−). H2O, constants between 31 28 were observed. systematic dependence rates on provides a small portion friction spectrum. A significant correlation solute IR absorption cross section solvent found, providing...

Increased long-term performance was found for photocatalytic H2 production in a homogeneous combination of [Re(NCS)(CO)3bipy] (1; bipy = 2,2′-bipyridine), [Co(dmgH)2] (dmgH2 dimethylglyoxime), triethanolamine (TEOA), and [HTEOA][BF4] N,N-dimethylformamide, achieving TONRe up to 6000 (H/Re). The system proceeded by reductive quenching *1 TEOA, followed fast (k1 1.3 × 108 M−1 s−1) electron transfer [CoII(dmgH)2] subsequent protonation (K2) elimination (k3, second-order process cobalt) H2....

The first photon echo peak shift study of liquid water is presented. Spectral diffusion within the OH stretching absorption band HDO in D2O takes place on many time scales with a slow component order 5−15 ps. This indicates that fluctuations local structure hydrogen bond network are relatively long-lived. Vibrational relaxation excited state populates which spectroscopically different from initial ground state. leads to an strong enhancement and allows spectral be measured for delay times...

Two-dimensional vibrational spectroscopy is applied to the amide I mode of trialanine and two its isotopomers dissolved in heavy water. We use site-directed 13C isotope substitution change individual frequencies coupled oscillators, hence modify specific matrix elements molecular Hamiltonian. It found that all results can be well described by an excitonic model for band, using same coupling strength dipole–dipole angle three isotopomers. This demonstrates these spectral parameters are...

The observation of subpicosecond fluctuations in the conformation a small peptide water is demonstrated. We use an experimental method that specifically sensitive to conformational dynamics taking place on ultrafast time scale. Complementary molecular-dynamics simulations confirm exhibit component, scale and amplitude which agree well with those derived from experiment.

We investigate energy transport through an α-aminoisobutyric acid-based 3 10 -helix dissolved in chloroform a combined experimental-theoretical approach. Vibrational is locally deposited at the N terminus of helix by ultrafast internal conversion covalently attached, electronically excited, azobenzene moiety. Heat flow detected with subpicosecond time resolution employing vibrational probes as local thermo meters various distances from heat source. The experiment supplemented detailed...

Photo-triggered α-helix formation of a 16-residue peptide featuring built-in conformational photoswitch is monitored by time-resolved IR spectroscopy. An experimental approach with 2-ps time resolution and scanning range up to 30 μs used cover all scales the dynamics. Experiments are carried out at different temperatures between 281 322 K. We observe single-exponential kinetics amide I′ band K on scale comparable recent temperature-jump folding experiment. When lowering temperature, become...

We present an artificial photocatalytic model for photosystem I (PSI) using [ReBr(CO)3bipy)] (1) as a photosensitizer, [Co(dmgH)2] (2) hydrogen evolution reaction catalyst, and triethanolamine irreversible reductive quencher. Complex 1 is more robust in the long run, turnover numbers were than doubled study compared to commonly used photosensitizer [Ru(bipy)3]2+. The quantum yield production with was found be 26 ± 2% (H produced per absorbed photon). Forward electron transfer between 1− 2...