Peptides experimental limitations

Proteins in foods such as milk have been the subject of much fluorimetric study involving measurement of the intrinsic fluorescence of tryptophan and tyrosine however, since proteins vary in their content of these amino acids, the fluorescence intensity also varies markedly from protein to protein and, for a single protein, with the experimental conditions. Also, the natural fluorescence of peptides is limited to peptide-containing tryptophans and tyrosines. However, the joint use of LC and derivatizing fluorogenic agents such as dansyl chloride, ninhydrin, fluorescamine, and o-phthaldialdehyde (OPA) has allowed the development of a number of methods for the determination of proteins, peptides, amino acids, and amines in food samples. 

Peptide Bond Synthesis Polypeptide Synthesis Experimental Limitations... 

Peptide bond formation is the essential reaction catalyzed by the ribosome. Despite its importance, it was for a long time not the focus of ribosomal research, for several reasons. First, before the determination of the high-resolution ribosome crystal structures almost nothing was known about the active site. Second, under most experimental conditions accommodation of the incoming aminoacyl-tRNA is rate limiting for peptide bond... 

Evidence of the involvement of CCK-B receptors in the neurobiology of anxiety has been strengthened by the findings that a closely related peptide, pentagastrin, produces dose-related and time-limited symptoms of social anxiety in both control subjects and patients with social phobia undergoing experimental social interactions (Uhde et al. 1993). Pentagastrin is a pentapeptide whose final tetrapeptide is identical to CCK-4. 

Even though these approaches are powerful methods for determining functional sites on proteins, they are limited if not coupled with some form of structural determination. As Figure 2 illustrates, molecular biology and synthetic peptide/antibody approaches are not only interdependent, they are tied in with structural determination. Structural determination methods can take many forms, from the classic x-ray crystallography and NMR for three-dimensional determination, to two-dimensional methods such as circular dichroism and Fourier Transformed Infrared Spectroscopy, to predictive methods and modeling. A structural analysis is crucial to the interpretation of experimental results obtained from mutational and synthetic peptide/antibody techniques. 

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