Temperature jump relaxation spectroscopy

Callendee, R., Dyee, R. B. (2002) Probing protein dynamics using temperature jump relaxation spectroscopy, Curr. Opin. Struct. Biol. 12, 628-633. 

TL2221). The mechanism of this proton transfer was also investigated using the temperature-jump relaxation technique (77JA4438). 3-Hydroxypyridine tautomer-ism has also been studied by magnetic circular dichroism spectroscopy (80BCJ3069). 

For these reactions, AG° 0. The experimental measurement of cross-reaction rates is generally more straightforward than the measurement of self-exchange rates. Either the reactants are simply mixed together, or a thermodynamically unstable system is generated rapidly (via pulse radiolysis, flash photolysis, or temperature-jump relaxation) to initiate the redox reaction. Absorption spectroscopy has almost always been used to monitor the progress of protein cross reactions. The primary goal of theory, as will become evident, is to provide a relationship between AG° and AG" " for cross reactions. 

Studies on the dynamics of complexation for guests with cyclodextrins have been carried out using ultrasonic relaxation,40 151 168 temperature jump experiments,57 169 183 stopped-flow,170,178,184 197 flash photolysis,57 198 202 NMR,203 205 fluorescence correlation spectroscopy,65 phosphorescence measurements,56,206 and fluorescence methods.45,207 In contrast to the studies with DNA described above, there are only a few examples in which different techniques were employed to study the binding dynamics of the same guest with CDs. This probably reflects that the choice of technique was based on the properties of the guests. The examples below are grouped either by a type of guest or under the description of a technique. 

T.L. Brown [109] studied the temperature dependence of the H-nmr resonance of the cobalt-bound methyl group and the C-nmr resonance of 90% C-enriched methylcobalamin. From analyses of the line shapes, the activation parameters for benzimidazole dissociation were calculated to be dG = 12.7 + 0.1 kcal/mole, AH = 11.1 +0.6 kcal/mole, and AS = —5.9 2.4 eu, leading to a calculated rate constant of 2060/sec at 25°C. In contrast, K.L. Brown and coworkers [110] studied the pH dependence of this reaction (Eqn. 63) at 5°C by temperature-jump spectroscopy and observed two relaxations, the faster of which (T / ca. 4.4 jusec) was pH-independent over the range pH 0.7-7.5 while the slower relaxation showed a slight pH dependence with a half-time of about 50 /tsec at pH 5.5-7.5 increasing to about 75 jusec at pH 1.6 and below. These authors assigned the faster relaxation to the reversible loss of water from the axial coordination position and the slower, pH-dependent relaxation to the reversible dissociation of benzimidazole, i.e. an S, l, or D mechanism (Eqn. 64). 

Eck V./Josef Holzwarth, A. Genz Iodine Laser Temperature J.F. Holzwarth, V. Eck, A. Genz, Iodine Laser Temperature Jump from Picoseconds to Seconds Relaxation Processes of Phospholipid Bilayers. In Bayley, P.M./R. Dale (Eds.), Spectroscopy and Dynamics of Biological Systems, London 1984, p. 351-377. 

An acetyl and an amide group block the N and C termini of the peptide chain. The tryptophan residue is added as a probe to collect time-resolved fluorescence signal under nanosecond T-jump spectroscopy, allowing measurement of coil to helix transition. The experimentally estimated relaxation time at room temperature for this transition is about 300 ns. The inverse of the experimental relaxation time is the sum of two rate constants, from the unfolded to the folded state and back. The equilibrium constant of this transition is about 1, which indicates that the forward and the backward rates are almost the same. The experimental first passage time from the folded to the unfolded state (which we estimate computationally in this chapter) is therefore 600 ns. This timescale seems achievable within the standard model and atomically detailed simulations. However, one should keep in mind that an ensemble of trajectories is required to study kinetics. The calculation of kinetics will be at least 100 times more expensive than the calculation of a single trajectory and therefore difficult to do with the usual standard model. 

Geometry and time scale of structural relaxation of poly(n-alkylmethacry-lates) above the glass transition is studied by temperature dependent ID and 2D C NMR spectroscopy. The geometry of the isotropisation of the polymer backbone as deduced from detailed analysis of spectral line shapes is identified as random angular jumps. Analysis of echo decays confirms that at a given temperature this isotropisation, can adequately be described with a single correlation time. ... 

Some of these parameters are directly measured with self-diffusion NMR spectroscopy (79, 80, 89) or indirectly by fluorescence probes (88). In addition, the relaxation of the microstructure after a sudden jump in a field variable such as temperature or pressure yields information on the dynamics of the structures (86). Depending upon composition of the mixtures, the time-scales of the dynamic processes range from microseconds to milliseconds (14, 88). 

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