Primary Reaction Intermediates of Type-I Photosensitized Lipid Oxidation as Revealed by Time-Resolved Optical Spectroscopies

2021 ◽  
pp. 113376
Author(s):  
Yi-Ming Zhou ◽  
Yan Zhang ◽  
Rong-Yao Gao ◽  
Wei Liu ◽  
Yuan Wei ◽  
...  
Keyword(s):  
Lipid Oxidation ◽  
Type I ◽  
Reaction Intermediates ◽  
Primary Reaction ◽  
Time Resolved

scholarly journals Visual Biochemistry: modular microfluidics enables kinetic insight from time-resolved cryo-EM

2020 ◽  
Author(s):  
Märt-Erik Mäeots ◽  
Byungjin Lee ◽  
Andrea Nans ◽  
Seung-Geun Jeong ◽  
Mohammad M. N. Esfahani ◽  
...  
Keyword(s):  
Sample Preparation ◽  
Reaction Intermediates ◽  
Protein Distribution ◽  
Time Resolved ◽  
Biochemical Processes ◽  
Molecular Events ◽  
Biophysical Analysis ◽  
Common Strategy ◽  
Set Up

AbstractMechanistic understanding of biochemical reactions requires structural and kinetic characterization of the underlying chemical processes. However, no single experimental technique can provide this information in a broadly applicable manner and thus structural studies of static macromolecules are often complemented by biophysical analysis. Moreover, the common strategy of utilizing mutants or crosslinking probes to stabilize otherwise short-lived reaction intermediates is prone to trapping off-pathway artefacts and precludes determining the order of molecular events. To overcome these limitations and allow visualisation of biochemical processes at near-atomic spatial resolution and millisecond time scales, we developed a time-resolved sample preparation method for cryo-electron microscopy (trEM). We integrated a modular microfluidic device, featuring a 3D-mixing unit and a delay line of variable length, with a gas-assisted nozzle and motorised plunge-freeze set-up that enables automated, fast, and blot-free sample vitrification. This sample preparation not only preserves high-resolution structural detail but also substantially improves protein distribution across the vitreous ice. We validated the method by examining the formation of RecA filaments on single-stranded DNA. We could reliably visualise reaction intermediates of early filament growth across three orders of magnitude on sub-second timescales. Quantification of the trEM data allowed us to characterize the kinetics of RecA filament growth. The trEM method reported here is versatile, easy to reproduce and thus readily adaptable to a broad spectrum of fundamental questions in biology.

Time-Averaged Quantity of a Low-Temperature Semiconductor Experiment Reflects Scaling Behavior of Saddle-Node Bifurcation to Chaos

1994 ◽  
Vol 49 (9) ◽  
pp. 838-842 ◽  
Author(s):  
R. Richter ◽  
A. Kittel ◽  
J. Paris
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Impact Ionization ◽  
Scaling Behavior ◽  
Type I ◽  
Saddle Node Bifurcation ◽  
Time Resolved ◽  
Saddle Node ◽  
Temperature Impact ◽  
P Type

Abstract Low-temperature impact ionization breakdown in p-type germanium crystals gives rise to spontaneous oscillations of the current flow. We demonstrate experimental evidence of a particularly high-conducting dynamical state that is limited to a finite parameter regime of the current versus magnetic field characteristic. After bifurcation from a coexisting nonoscillatory state to periodicity, one observes a type-I intermittent transition to chaos and, eventually, a jump back to the nonoscil­latory branch upon increasing the magnetic field control parameter. The scaling behavior of the underlying saddle-node bifurcation, already found in time-resolved measurements, also becomes visible in a square-root dependence of the time-averaged current developing both prior to and after the critical point. Our result might be of interest for time-averaged information is accessible.

Time-Resolved Gain Spectroscopy on Type-I and Type-II VECSEL Chips

2016 ◽  
Author(s):  
Christian Lammers ◽  
Markus Stein ◽  
Melanie Fey ◽  
Christoph Möller ◽  
Christian Fuchs ◽  
...  
Keyword(s):  
Type I ◽  
Type Ii ◽  
Time Resolved

Photosensitization by chiral drugs: Looking for stereodifferentiating photoprocesses in the presence of biomolecules

2005 ◽  
Vol 77 (6) ◽  
pp. 995-1000
Author(s):  
Virginie Lhiaubet-Vallet
Keyword(s):  
High Performance ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Single Strand ◽  
Type I ◽  
Chiral Drugs ◽  
Time Resolved ◽  
Strand Breaks ◽  
Single Strand Breaks

Photoreactivity of chiral carprofen (CP) and ofloxacin in the presence of two biomolecules, namely, DNA and human serum albumin (HSA), has been reported. Analysis of the photosensitization of 2'-deoxyguanosine and thymidine (Thd) by high-performance liquid chromatograpy has shown that racemic ofloxacin and levofloxacin [its (S)-stereoisomer] acts by a mixed type I/type II mechanism, while CP does not lead to significant degradation of the nucleosides. Studies on DNA relaxation have revealed formation of single-strand breaks and specific alterations of DNA bases. Ofloxacin and levofloxacin photoinduce direct single-strand breaks and formation of purine and pyrimidine oxidative photoproducts; no Thd dimer has been detected. CP produces only photosensitized single-strand breaks. Moreover, DNA photosensitization has shown a weak enantiodifferentiation in favor of levofloxacin and (S)-CP. In the case of HSA, a remarkable stereodifferentiation has been found in the interaction between the excited triplet state of CP and protein. Time-resolved laser flash photolysis measurements revealed the presence of two components with different lifetimes that have been assigned to complexation of CP to the two binding sites of albumin. Moreover, photobinding of the drug to protein and formation of the dehalogenated photoproduct of CP proceed via stereodifferentiating photoprocesses.

Time-resolved IR characterization of cis- and trans-[LW(CO)4(solvent)] [L = PPh3, P(OCHMe2)3, and P(OEt)3] in n-heptane solution. The solvent as a token ligand in short-lived reaction intermediates

1987 ◽  
Vol 109 (14) ◽  
pp. 4218-4224 ◽  
Author(s):  
Gerard R. Dobson ◽  
P. Michael Hodges ◽  
Michael A. Healy ◽  
Martyn Poliakoff ◽  
James J. Turner ◽  
...  
Keyword(s):  
Reaction Intermediates ◽  
Time Resolved ◽  
Cis And Trans

Rheo-Optical Study of Polymers by Using Time-Resolved Soft-Pulse Compression Attenuated Total Reflection Step-Scan Fourier Transform Infrared Spectroscopy

2009 ◽  
Vol 63 (11) ◽  
pp. 1204-1210 ◽  
Author(s):  
Yuji Nishikawa ◽  
Tatsuhiko Nakano ◽  
Isao Noda
Keyword(s):  
Fourier Transform ◽  
Pulse Compression ◽  
Dynamic Compression ◽  
Pulse Frequency ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Type I ◽  
Type Ii ◽  
Time Resolved ◽  
2D Ir

A time-resolved soft-pulse dynamic compression attenuated total reflection (ATR) step-scan Fourier transform rheo-optical system has been developed. This system was used to observe different viscoelastic properties of polyethyleneterephthalate (PET) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx). Resonance features were observed in the dynamic compression ATR spectrum of PHBHx with 625 Hz soft-pulse frequency. In contrast, the dynamic compression ATR spectrum of PET showed no resonance features. The resonance feature of PHBHx was found at 1723 cm−1, which corresponds to the structural or morphological reorganization of a less ordered (Type II) crystalline form under compressive perturbation. The time-resolved evolution of infrared (IR) spectra was effectively analyzed by conventional generalized two-dimensional (2D) correlation analysis. The 2D-IR results indicate that the dynamic response of the well-ordered Type I crystalline state (1289 and 1261 cm−1) is faster than that of the Type II (1723, 1277, and 1228 cm−1). The present method shows promise for characterizing a wide variety of viscoelastic materials, including polymer alloys, blends, composites, and copolymers, and semicrystalline polymers.

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