Proton chemical shifts polypeptides

Advances in NMR instrumentation and methodology have now made it possible to determine site-specific proton chemical shift assignments for a large number of proteins and nucleic acids (1,2). It has been known for some time that in proteins the "structural" chemical shifts (the differences between the resonance positions in a protein and in a "random coil" polypeptide (3-5),) carry useful structural information. We have previously used a database of protein structures to compare shifts calculated from simple empirical models to those observed in solution (6). Here we demonstrate that a similar analysis appears promising for nucleic acids as well. Our conclusions are similar to those recently reported by Wijmenga et al (7),... 

Conformational analysis of polypeptides based on a-proton chemical shifts... 

Therefore, it was proved that a H CRAMPS method which combines higher MAS speed (3.5 kHz) with MREV-8 pulse spectroscopy is a very useful tool for the determination of NH proton chemical shifts in solid polypeptides. 

The NH proton chemical shifts of some polypeptides were successfully determined using fully N-labelled samples at a higher MAS frequency with a MREV-8 pulse sequence. The NH proton chemical shifts determined with the... 

In conclusion, it is certified that the NH proton chemical shift is a useful index for conformational analysis and to distinguish the hydrogen bond characteristics of polypeptides in the solid state. 

The i N H -NOEs can also be presented in a two-dimensional spectrum, using tbe [ N, H]-COSY-relayed i N H -NOE experiment. Positive and negative cross-peaks may then be displayed in separate subspectra (Fig. 6, B and C), which affords a nice illustration of the different dispersion of the chemical shifts in the unfolded and folded parts of the protein (Wuthrich, 1986). The spectrum of Fig. 6B is typical for a globular domain, with the backbone amide proton chemical shifts spread out from 7 to 10 ppm, and the spectrum of the tail in Fig. 6C contains backbone amide proton peaks only between 8.0 and 8.7 ppm, wbicb is typical for an extended random coil polypeptide chain. 

A study example concerning the solid structure of a-amino acid, polypeptide and a protein is given to introduce the basis of the chemical shift of proton NMR precisely, and studies to do this have only recently been undertaken. Some interesting work has been done, including the discrimination of amino acid crystal polymorphism, conformational analysis of polypeptides and fibrous proteins, and the determination of the N—H bond length in polypeptides. 

Most recently, it has been reported that there is a large difference in solid-state chemical shifts between the a-helix and j8-sheet for polypeptides as shown in Fig. 22.3 [7j. In (Ala) , the chemical shift of the C H proton for the a-helix form appears at lower frequency by 1.2-1.4 ppm than for the j8-sheet form. The NH proton signal is very broad due to the quadrupolar interaction with the nucleus. In (Leu) and (Glu(OBzl)) , it was found that similar behavior exists. 

In the investigations of hPrP, special efforts have been made to characterize conformational equilibria in the less precisely structured polypeptide segments by studies of the chemical shifts and measurements of amide proton protection factors (Hosszu et al, 1999 Zahn et al., 2000). In contrast to the NOE intensity, which depends on the inverse sixth power of the distance and therefore usually... 

Membranes and model membranes exhibit liquid crystalline behavior and this has been exploited in a number of studies to obtain valuable information on the structure and dynamics of membrane associated peptides and proteins as well as on the interaction of the peptides with the membranes themselves. NMR spectroscopy of nuclei such as proton, carbon, deuterium, nitrogen and phosphorus has been utilized for such purposes. Structure elucidation of membrane-associated peptides and proteins in oriented bilayers by solid-state NMR spectroscopy has been reviewed. A survey on the use of static uniaxially oriented samples for structural and topological analysis of membrane-associated polypeptides is available. The theoretical background has been dealt with and a number of examples of applications provided. In addition, ongoing developments combining this method with information from solution NMR spectroscopy and molecular modelling as well as exploratory studies using dynamic nuclear polarization solid-state NMR have been presented. The use of N chemical shift anisotropy, dipolar interactions and the deuterium quadrupolar split-... 

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