Temperature jump nanosecond

This report has been written in order to demonstrate the nature of spin-state transitions and to review the studies of dynamical properties of spin transition compounds, both in solution and in the solid state. Spin-state transitions are usually rapid and thus relaxation methods for the microsecond and nanosecond range have been applied. The first application of relaxation techniques to the spin equilibrium of an iron(II) complex involved Raman laser temperature-jump measurements in 1973 [28]. The more accurate ultrasonic relaxation method was first applied in 1978 [29]. These studies dealt exclusively with the spin-state dynamics in solution and were recently reviewed by Beattie [30]. A recent addition to the study of spin-state transitions both in solution and the... 

As better and better methods for following fast reactions with precision were introduced and exploited, characteristic reaction times faster than a second— times measured in milhseconds (ms, 10 s), or microseconds (ps, 10 s), or nanoseconds (ns, 10 s) and then in picoseconds (ps, 10 s)—were measured through stopped-flow techniques (Chance, 1940), flash photolysis (Norrish and Porter, 1949), temperature-jump and related relaxation methods (Eigen, 1954), and then... 

At present we are far from an understanding of the protein folding process. Even numerical methods as e.g. molecular dynamics simulations do not lead to realistic predictions. Experiments on the folding process have been performed initially on the millisecond time-scale. It was only recently that new techniques - temperature jump or triplet-triplet quenching experiments - allowed a first access to the nanosecond time domain [2-4]. However, the elementary reactions in protein folding occur on the femto- to picosecond time-scale (femtobiology). In order to allow experiments in this temporal range we developed a new... 

Holzwarth, J. F., A. Schmidt, H. Wolff, and R. Volk. 1977. Nanosecond temperature-jump technique with an iodine laserJ. Phys. Cherrfil 2300-2301. 

Various kinetic methods in the enzyme catalysis has been described elsewhere (Likhtenshtein, 1988a Gates, 1991 Bugg, 1997 Comish-Bowden, 1995, 2001 Varfolomeev and Gurevich, 1998) Fersht,1999 Gutfreund,. 1995 Hammes, 2000 Leninger et al.1993 ). In this section we concentrate on recent developments in methods of the kinetic isotope effect, transition state analoges, and nanosecond temperature jump techniques. 

A nanosecond temperature jump is induced by an illumination of a sample with the laser heat pump. For instance, in the work of Yamamoto et al. (2000) the 1.56-pm heat pulse 9 ns width at 10 Hz was obtained through the two-step stimulating Raman scattering in D2 gas. 

Yamamoto, K., Mizutani, Y., and Kitagawa, T. (2000) Nanosecond temperature jump and time-resolved Raman study of thermal unfolding of ribonuclease A, Biophys. J. 79, 485-495. 

The time scale of the classical temperatine-jnmp experiment ( 1 qs) as originally pioneered by Eigen has been shortened to nanoseconds and very recently to approximately 5 ps using lasers. The classical temperatnre-jump experiment has found only limited application to biological systems, in spite of its great success in determining, for example, proton transfer rates or keto-enol isomerizations. An important reason for its limited apphcation to enzyme research, apart from experimental difficulties such as optical artifacts as a result of the temperature-jump, is the relatively small deviation from equihbrium AG = AH —... 

The laser temperature jump instrument can effectively be used to initiate and observe the fast events in protein/peptide folding and unfolding as well as those events that extend out to several milliseconds. In the present study, the unfolding of a helical peptide was determined to occur within tens of nanoseconds, supporting the need for nanosecond or faster initiation techniques. Promising results obtained by the laser temperature jump method will continue to stimulate the development of additional monitoring techniques such as UV absorption and circular dichroism. 

An important turning point in reaction kinetics was the development of experimental techniques for studying fast reactions in solution. The first of these was based on flow techniques and extended the time range over which chemical changes could be observed from a few seconds down to a few milliseconds. This was followed by the development of a variety of relaxation techniques, including the temperature jump, pressure jump, and electrical field jump methods. In this way, the time for experimental observation was extended below the nanosecond range. Thus, relaxation techniques can be used to study processes whose half lives fall between the range available to classical experiments and that characteristic of spectroscopic techniques. 

Picosecond laser pulses in the UV range do not result in better ablation behavior than nanosecond laser pulses. This is different for doped polymers. Experiments with doped PMMA (an IR-absorber, i.e., IR-165 for ablation with near-IR laser and diazomeldrum s acid (DMA) for ablation with UV lasers) with nanosecond and picosecond laser irradiation in the UV (266 nm) and near-IR (1064 nm) range have shown that, in the IR, neat features could be produced with picosecond laser irradiation, while nanosecond irradiation only results in rough surface features [105]. This corresponds well with the different behavior of the two absorbers. With IR-165 the polymer is matrix is heated by a fast vibrational relaxation and multiphonon up-pumping [106]. This leads to a higher temperature jump for the picosecond irradiation, which causes ablation, while for nanosecond pulses only lower temperatures are reached. 

Chung, H.S., Khalil, M., Smith, A.W., and Tokmakoff, A. (2007) Transient two-dimensional IR spectrometer for probing nanosecond temperature-jump kinetics. Rei>. Sci. Instrum., 78, 063101. 

Transient intermediates are most commonly observed by their absorption (transient absorption spectroscopy see ref. 185 for a compilation of absorption spectra of transient species). Various other methods for creating detectable amounts of reactive intermediates such as stopped flow, pulse radiolysis, temperature or pressure jump have been invented and novel, more informative, techniques for the detection and identification of reactive intermediates have been added, in particular EPR, IR and Raman spectroscopy (Section 3.8), mass spectrometry, electron microscopy and X-ray diffraction. The technique used for detection need not be fast, provided that the time of signal creation can be determined accurately (see Section 3.7.3). For example, the separation of ions in a mass spectrometer (time of flight) or electrons in an electron microscope may require microseconds or longer. Nevertheless, femtosecond time resolution has been achieved,186 187 because the ions or electrons are formed by a pulse of femtosecond duration (1 fs = 10 15 s). Several reports with recommended procedures for nanosecond flash photolysis,137,188-191 ultrafast electron diffraction and microscopy,192 crystallography193 and pump probe absorption spectroscopy194,195 are available and a general treatise on ultrafast intense laser chemistry is in preparation by IUPAC. 

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