Nuclear magnetic resonance protein preparation

Retention of a protein or protein activity after 105,000y, 1 hr Chromatography on gel filtration columns with large pore sizes Electron microscopy—however, sample preparation may partially reconstitute membranes Decrease in solution turbidity, which may be detected by a diminution in light scattering or an enhancement in light transmission Diffusion of membrane lipids as assayed by nuclear magnetic resonance and electron spin resonance... 

This chapter describes protocols for preparing 15N-labeled proteins (ubiquitin is used as an example) using Escherichia coli cells (with purification) and the wheat germ cell-free system (without purification). A comparison of I I-15N heteronuclear single-quantum coherence (HSQC) spectra of yeast ubiquitin prepared using each method indicates that this wheat germ cell-free system may be used for rapid nuclear magnetic resonance analyses of proteins without purification. 

Spectrometric Analysis. Remarkable developments in mass spectrometry (ms) and nuclear magnetic resonance methods (nmr), eg, secondary ion mass spectrometry (sims), plasma desorption (pd), thermospray (tsp), two or three dimensional nmr, high resolution nmr of soHds, give useful stmcture analysis information (131). Because nmr analysis of or N-labeled amino acids enables deterrnination of amino acids without isolation from organic samples, and without destroying the sample, amino acid metaboHsm can be dynamically analyzed (132). Protein metaboHsm and biosynthesis of many important metaboHtes have been studied by this method. Preparative methods for labeled compounds have been reviewed (133). 

Page RC, Moore JD, Nguyen HB, Shatma M, Chase R, Gao FP, Mobley CK, Sanders CR, Ma L, Sonnichsen FD, Lee S, Howell SC, Opella SJ, Cross TA (2006) Comprehensive evaluation of solution nuclear magnetic resonance spectroscopy sample preparation for helical integral membrane proteins. J Struct Funct Genomics 7 51-64... 

There were also attempts to calibrate the SEC columns with help of broad molar mass dispersity poplymers but this is less lehable. The most common and well credible SEC cahbration standards are linear polystyrenes, PS, which are prepared by the anionic polymerizatioa As indicated in section 11.7, according to lUPAC, the molar mass values determined by means of SEC based on PS calibration standards are to be designated polystyrene equivalent molar masses . Other common SEC calibrants are poly(methyl methaciylate)s, which are important for eluents that do not dissolve polystyrenes, such as hexafluoroisopropanol, further poly(ethylene oxide)s, poly(vinyl acetate)s, polyolefins, dextrans, pullulans, some proteins and few others. The situation is much more complicated with complex polymers such as copolymers. For example, block copolymers often contain their parent homopolymers (see sections 11.8.3, 11.8.6 and 11.9). The latter are hardly detectable by SEC, which is often apphed for copolymer characterization by the suppliers (compare Figure 16). Therefore, it is hardly appropriate to consider them standards. Molecules of statistical copolymers of the same both molar mass and overall chemical composition may well differ in their blockiness and therefore their coils may assume distinct size in solution. In the case of complex polymers and complex polymer systems, the researchers often seek support in other characterization methods such as nuclear magnetic resonance, matrix assisted desorption ionization mass spectrometry and like. 

The fidelity of the protein-based polymer expression from a prepared gene is extraordinary when compared to the chemically prepared product. Even so, it is important to use purification procedures that limit alteration of the structure and to establish that proteolytic or other enzymatic activity is sufficiently limited that the desired properties of the expressed protein-based polymer are retained. An important method with which to achieve adequate verification of the gene product again utilizes multi-dimensional nuclear magnetic resonance. 

C. R. Sanders, Membrane protein preparation for TROSY NMR screening. In Nuclear Magnetic Resonance of Biological Macromolecules, Part C, 2005, vol. 394, pp. 321-334. 

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