Polypeptides characterization

Full-scale polypeptide characterization usually requires modest/large (milligram to gram) amounts of the purified target polypeptide. Even larger quantities are then generally required... 

Leski, M.L. and Steward, 0. (1996) Protein synthesis within dendrites ionic and neurotransmitter modulation of synthesis of particular polypeptides characterized by gel electrophoresis. Neurochem. Res. 22,681-690. 

Wu A., Harriman R.W, Frost D.J., Read S.M., and Wasserman B.P. 1991. Rapid enrichment of CHAPS-solubilized UDP-glucose (l->3)-P-glucan (callose) synthase from Beta vulgaris L. by product entrapment. Entrapment mechanisms and polypeptide characterization. Plant Physiol 97 684-692. 

At present, the term kinin is a generic name for polypeptides characterized by the following biological effects lowering of blood pressure, contraction of most smooth-muscle preparations, increase of capillary permeability, pain production and bronchoconstiiction in the guinea-pig. The reader is reminded that the nomenclature of this group of substances and of the enzymes which liberate them, as well as the enzymes which inactivate them, is not uniforuL In this chapter, the recommendations of the Committee on Nomenclature for Hypotensive Peptides have been followed... 

The amide linkage between monomer units in a protein is called a peptide bond. Peptides and polypeptides, which often exhibit biological activity (see Antibiotics, peptides Neuroregulators), are smaller than proteins. Although the differentiation between polypeptide and protein is somewhat arbitrary, the usual distinction is drawn around 100 monomer units. Proteins are also characterized by higher levels of stmcture resulting from internal interactions. 

Figures 13.54 thru 13.56 have been singled for special mention because of the unusual nature of the applications presented. Because peptides are also polyamides and because we routinely run polyamides using hexafluoro-2-pro-panol (FIFIP) as solvent, a modified polypeptide, poly (leucine-comethyl glutamate), was run in FIFIP. Figure 13.54 shows the results and suggests that modified HFIP might well prove to be a good solvent for at least some polypeptide purifications/characterizations. Figure 13.55 demonstrates the use of modi-...

The structures of amino acids incorporated into polypeptides and proteins may be characterized by a pair of dihedral angles involving the so-called a carbon for each amino acid. 

Classical gel electrophoresis has been used extensively for protein and nucleic acid purification and characterization [9, 10], but has not been used routinely for small molecule separations, other than for polypeptides. A comparison between TLC and electrophoresis reveals that while detection is usually accomplished off-line in both electrophoretic and TLC methods, the analyte remains localized in the TLC bed and the mobile phase is immediately removed subsequent to chromatographic development. In contrast, in gel electrophoresis, the gel matrix serves primarily as an anti-... 

This complex consists of at least 25 separate polypeptides, seven of which are encoded by mtDNA. Its catalytic action is to transfer electrons from NADH to ubiquinone, thus replenishing NAD concentrations. Complex I deficiency has been described in myopathic syndromes, characterized by exercise intolerance and lactic acidemia. In at least some patients it has been demonstrated that the defect is tissue specific and a defect in nuclear DNA is assumed. Muscle biopsy findings in these patients are typical of those in many respiratory chain abnormalities. Instead of the even distribution of mitochondria seen in normal muscle fibers, mitochondria are seen in dense clusters, especially at the fiber periphery, giving rise to the ragged-red fiber (Figure 10). This appearance is a hallmark of many mitochondrial myopathies. 

HSFl phosphorylation must be sensitive to nonheat inducers of HSF-DNA binding activity because HSFl phosphorylation can be achieved at 37 °C by other inducers of the HS response. HSF 1 contains polypeptide sequences that could serve as substrates for well characterized protein kinases, but few of these are known to be heat inducible. One family of protein kinases, the S6 protein kinases, have already been shown to exhibit heat inducible activity however, their peak level of activity during HS occurs well after the maximal induction of HSF phosphorylation (Jurivich et al., 1991). Thus, other protein kinases are likely to be directly linked to the phosphorylation of HSF. Some of the putative protein phosphorylation sites on HSF include motifs for protein kinase C, casein kinase, and enterokinase. There are tyrosine sequences that match substrates for known tyrosine kinases, but whether these residues are accessible to phosphorylation is not established. 

Three ferredoxins were isolated and characterized fromZ). africanus. The proteins are dimers of subunits with a molecular mass of circa 6 kDa. D. africanus Fdl contains a single [4Fe-4S] center bound to a polypeptide structure of 60 amino acids with only 4 cysteines. This is the minimal requirement for [4Fe-4S] cluster binding. D. africanus Fdll is a minor component, not so well characterized, and seems to contain a [4Fe-4S] center (68, 69). Fdlll of this strain is a dimer containing 61 amino acids and 7 cysteine residues per subunit. The protein contains a [3Fe-4S] and a [4Fe-4S] cluster (70-72). 

D. desulfuricans is able to grow on nitrate, inducing two enzymes that responsible for the steps of conversion of nitrate to nitrite (nitrate reductase-NAP), which is an iron-sulfur Mo-containing enzyme, and that for conversion of nitrite to ammonia (nitrite reduc-tase-NIR), which is a heme-containing enzyme. Nitrate reductase from D. desulfuricans is the only characterized enzyme isolated from a sulfate reducer that has this function. The enzyme is a monomer of 74 kDa and contains two MGD bound to a molybdenum and one [4Fe-4S] center (228, 229) in a single polypeptide chain of 753 amino acids. FXAFS data on the native nitrate reductase show that besides the two pterins coordinated to the molybdenum, there is a cysteine and a nonsulfur ligand, probably a Mo-OH (G. N. George, personal communication). 

Elastomeric polypeptides are a class of very interesting biopolymers and are characterized by mbber-like elasticity, large extensibility before rupture, reversible deformation without loss of energy, and high resilience upon stretching. Their useful properties have motivated their use in a wide variety of materials and biological applications. Here, we focus on two elastomeric proteins and the recombinant polypeptides derived thereof. 

Historically, after the development of oligopeptide-based vesicles, several groups developed and characterized vesicles using polypeptide hybrid systems consisting of polypeptide and synthetic polymer blocks [17-19]. Soon thereafter, vesicles formed entirely from polypeptides, such as poly(L-lysine)-h-poly(L-leucine) and poly(L-lysine)-h-poly(L-glutamate), were developed [20, 21]. This review will focus on recent developments in the formation of vesicles composed of polypeptide hybrid or polypeptide systems, as well as the potential promise of these systems as effective dmg delivery vehicles. A specific example of a polypeptide-based vesicle is shown in Fig. 1, where the hydrophobic segment is a-helical and the hydrophilic segment is a random coil. 

Many techniques used in other fields have been adapted to visualize and characterize vesicles composed of polypeptide and polypeptide hybrid systems. This section will describe these different approaches. 

McMillan RA, Conticello VP (2000) Synthesis and characterization of elastin- mimetic protein gels derived from a well-defined polypeptide precursor. Macromolecules 33 4809 821... 

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