Correspondence

Date:
1968-1969
Reference:
PP/CRI/E/1/17/4/2
Catalogue details

Licence: In copyright

Credit: Correspondence. Source: Wellcome Collection.

    37/56
    This is, what is the chemical identity of reaction intermediates, and what is the chemistry of the kinetic steps leading to and from these intermediates? Methods are therefore required to investigate the environment of atoms or groups of enzyme and substrate while these are in contact. The application of such spectroscopic techniques as n.rn.r. and e.s.r. to enzyme mechanisms has in the last f ew years shown the way in which the conceptual gap between structural, information and kinetic information may be closed. Proton magnetic resonance spectroscopy has particular applications to the study of individual residues in proteins, (e.g. the work of W.D. Phillips, and of Jardetsky) and can be used as a powerful probe of active site phenomena in metallo-enzymes (e.g. the work of M. Cohn). There are two major problems in the use of n.m.r. techniques in protein chemistry. First, the fact that since all protons in the system give rise to resonance peaks, a very considerable overlapping of peaks occurs. This problem can be reduced by working at higher magnetic fields, when the absorption spectrum i3 spread out, and the resonances from protons in slightly different environments can be distinguished. The 220 MHz n.m.r. spectrometer has already shown its capabilities in this respect, and - for instance - the N-H protons of each of the six tryptophan residues of lysozyme have been discerned separately by W.D. Phillips using such an instrument. Many of the Panel's respondents stressed the potentiality of very high field n.m.r. for working on enzymological problems. The second problem is one of sensitivity, which sets an upper limit on the molecular weight of materials which can be studied with present instruments. This barrier is steadily being pushed back, largely by improvements in instrument design, and the present effective upper limit is high enou^i now to allow the study of a very large number of proteins. Other problems of particular importance in enzyme chemistry which can be studied with high precision by n.m.r. include: protein folding and unfolding, sites of binding of substrates, and of inhibitors (using H*, P^ 1 , C^); metal binding phenomena by