Peptide theory

The second aspect refers to the protein nature of enzymes. In 1894 Fischer (Fischer, 1909) stated that amongst the agents which serve the living cell the proteins are the most important. He was convinced that enzymes are proteins. The role of this key problem may be illustrated with a citation from Fruton (1979) ... the peptide theory was indeed only a hypothesis fifty years after Franz Hofmeister and Emil Fischer advanced it... (in 1902). The nature and stracture of proteins remained unknown throughout the 19th century remarkably, technological applications were nevertheless put into practice since the middle of the century (see above), based on their action, eventually recognized as catalysis, only. 

Peptide samples Mass of expected peptides Theory Found Mass found in unknown species AMass between expected and unknown peptides... 

As an initial working hypothesis it will be assumed that the peptide theory is valid, in other words, that a protein molecule is built up only of chains of a-amino (and a-imino) acids bound together by peptide bonds between their a-amino and a-carboxyl groups. While this peptide theory is almost certainly valid (see Vickery and Osborne, 1928 Pauling and Niemann, 1939 Synge, 1943), it should be remembered that it is still a hypothesis and has not been definitely proved. Probably the best evidence in support of it is that since its enunciation in 1902 no facts have been found to contradict it. It is to be expected that investigations of the types described in the present article will throw further light on the accuracy of the peptide theory and on the possible existence of nonpeptide bonds in proteins. 

T Nonequilibrium Molecular Dynamics Simulation of Photoinduced Energy Flow in Peptides Theory Meets Experiment... 

McLaughlin, Biophys. J., 77, 3176 (1999). Electrostatic Properties of Membranes Containing Acidic Lipids and Adsorbed Basic Peptides Theory and Experiment. 

Charloteaux B, Lorin A, Brasseur R, lins L. The "TQted Peptide Theory" links membrane insertion properties and fusogenicity of viral fusion peptides. Protein Pept Lett. 2009 16(7) 718-725. 

The Peptide Theory (Hofmeister and Emil Fischer).— The protein molecule is a chain composed of peptide links, and has the type formula —... 

Evid .nce in Support of the Peptide Theory.—(i.) All proteins give a violet or rose colour with copper salts in alkaline solution (the copper protein test), which is characteristic of the peptide linkage =CH —CO—NH—CH=, and not given by any individual amino acid other than serine, threonine and histidine, which have a somewhat similar arrangement in their molecules. 

Developments of the Peptide Theory.—(a) lattice Stmcture.— When a crystal is irradiated by X-rays, secondary rays are reflected from each surface within the structure, and form interference patterns that can be photographed. From a study of these patterns, Astbury concludes that proteins have a lattice structure owing to transverse association between alternate CO and NH groups in the peptide chain. 

B. Compartmentation of Secretory Proteins—The Signal Peptide Theory... 

Although the precise mechanism of plasminogen activation is unknown, three principal theories have developed based on studies of the in vitro activation of native human plasminogen. Activation of native Glu-plasminogen in the absence of any plasmin inhibitor yields Lys —plasmin plus the so-called pre-activation peptides (PAP) formed by cleavage at LySg2 S E3 Activation takes place by a two-step mechanism in... 

One important class of integral equation theories is based on the reference interaction site model (RISM) proposed by Chandler [77]. These RISM theories have been used to smdy the confonnation of small peptides in liquid water [78-80]. However, the approach is not appropriate for large molecular solutes such as proteins and nucleic acids. Because RISM is based on a reduction to site-site, solute-solvent radially symmetrical distribution functions, there is a loss of infonnation about the tliree-dimensional spatial organization of the solvent density around a macromolecular solute of irregular shape. To circumvent this limitation, extensions of RISM-like theories for tliree-dimensional space (3d-RISM) have been proposed [81,82],... 

OM Becker, M Karplus. The topology of multidimensional potential energy surfaces Theory and application to peptide stiaicture and kinetics. I Chem Phys 106 1495-1517, 1997. 

Righetti, P.G., Gelfi, C., Perego, M., Stoyanov, A.V., and Bossi, A., Capillary zone electrophoresis of oligonucleotides and peptides in isolectric buffers theory and methodology, Electrophoresis, 18, 2145, 1997. 

We now want to turn to another experiment which, we must make clear at the start, does not have any relationship in theory to NOE experiments. In fact the theory is so complicated that we shall not say anything about it at all, but just refer you to one of the books in the Appendix. We are including this experiment because of its unique advantages when the spectrum has overlapping multiplets. It is called TOCSY, which stands for Total Correlation SpectroscopY (it has a second, more amusing name HOHAHA, standing for HOmonuclear HArtmann-HAhn), and is of particular use when oligosaccharides or peptides are under study. 

Three theory papers are also included. Determinants of the Polyproline II Helix from Modeling Studies by Creamer and Campbell reexamines and extends an earlier hypothesis about Pn and its determinants. Hydration Theory for Molecular Biophysics by Paulaitis and Pratt discusses the crucial role of water in both folded and unfolded proteins. Unfolded State of Peptides by Daura et al. focuses on the unfolded state of peptides studied primarily by molecular dynamics. 

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