Derivatives of proteins

Hydrazide groups can react with carbonyl groups to form stable hydrazone linkages. Derivatives of proteins formed from the reaction of their carboxylate side chains with adipic acid dihydrazide (Chapter 4, Section 8.1) and the water-soluble carbodiimide EDC (Chapter 3, Section 1.1) create activated proteins that can covalently bind to formyl residues. Hydrazide-modified enzymes prepared in this manner can bind specifically to aldehyde groups formed by mild periodate oxidation of carbohydrates (Chapter 1, Section 4.4). These reagents can be used in assay systems to detect or measure glycoproteins in cells, tissue sections, or blots (Gershoni et al., 1985). 

Figure 6.15. Structures of some protein kinase C inhibitors. Staurosporine is a potent inhibitor of protein kinase C, but is not selective. Some derivatives of protein kinase C, such as Ro31-8220 and Ro31-8425, retain a potency similar to that of the parent molecule in protein kinase C inhibition, but are much more specific.

In the personal care market, fatty acid derivatives of proteins and amino acids (glutamic acid) are mainly used in mild shower and bath products, mild shampoos, surfactant-based face cleansers, cold-wave preparations and fixatives, baby wash formulations, as well as special emulsifiers for leave-on products. 

Dansyl Chloride (afluorotag) is invariably used to obtain fluorescent derivatives of proteins, amines and phenolic compounds, the excitation and emission wavelengths being 335 to 365 nm and 520 nm respectively. 

In the human CNS, glutamate is the most important excitatory neurotransmitter. Glycine is a major inhibitory neurotransmitter in the human CNS. Thus, these two amino acids, basic constituents of proteins, also function in other very important ways in behavior, emotion, learning, memory, and sensory perception. Nature uses its molecular constructs for more than one purpose. Among other neurotransmitters, dopamine, epinephrine, norepinephrine, and serotonin are derivatives of protein amino acids and are synthesized from them. 

Since a common route to 3Fe derivatives of proteins containing 4Fe-4S clusters is via oxidation (34), this implies that it might be possible to prepare a synthetic 3Fe-4S cluster by simple oxidation of an [Fe S L ] " cluster. A recent attempt to implement this strategy examined oxidation of [Fe SA(S-t-Bu)4] by ferricyanide in DMF/H2O solution at T < -40°C (35). Although a species with EPR and Mossbauer parameters similar to those of protein-bound 3Fe centers was generated (in < 30% yield), it was... 

In 1938 it was found that organotin derivatives of proteins and nucleoproteins and the products of their hydrolysis could be used to treat some skin and blood diseases1068,1069. 

In view of the large amount of literature which has accumulated on the preparation, properties, and analysis of derivatives of proteins, a few comments on the problems encountered on acid hydrolysis of these substances are warranted. 

Fig. 7. Electrophoresis diagram of SCM derivatives of proteins extracted from feather (a) rachis, (b) calamus, (c) barbs, and (d) medulla (Harrap and Woods, 1964a).

A number of studies have been performed with methyl picolinimidate (Benisek and Richards 1968 Plapp et al. 1971) aimed at exploring the usefulness of the metal-chelating properties of such derivatives in the preparation of isomorphous heavy atom derivatives of proteins for X-ray diffraction studies. 

The second approach is to redefine the nutrient medium itself so that each component is at its optimal concentration for the cell line of interest. This is a more difficult and tedious process than the first, but it provides the balanced nutrient medium necessary for derivation of protein-free growth conditions. To derive the balanced nutrient medium, start with a low serum concentration at which there is reduced cell growth. Then systematically titrate each component in the medium to determine its optimal growth-promoting concentration. After... 

One of the most useful experimental methods to be applied to protein adsorption in recent years is the radiotracer technique (Mura-matsu, 1973). Proteins labeled with, 31I and 125I (Brash et al., 1974) and [14C]acetyl derivatives of proteins (Phillips et al., 1975) have been used as tracers. As well as measuring adsorption directly, this method has the great advantage that it can detect exchange between interface and bulk even when the total amount adsorbed does not vary. A technique that has been used to obtain independent measurements of the amount of protein adsorbed by measuring film thickness is ellipsometry (Trurnit, 1953). 

Pathophysiology Acetaminophen is metabolized via the cytochrome P450 enzymes into a deleterious product A-acetyl benzoquinoneimine, an unstable intermediate, which causes arylated derivatives of protein, lipid, ribonucleic acid (RNA), and deoxyribonucleic acid (DNA), causing destruction of these compounds. Because the Uver has high levels of cytochrome P450 enzymes, it is the major organ affected by acetaminophen overdose. 

J. F. Brinkley, R. B. Altman, B. S. Duncan, B. G. Buchanan, and O. Jardetzky. 1988. Heuristic refinement method for the derivation of protein solution structures validation on cytochrome b562. Journal of Chemical Information and Computer Sciences 28(4) 194-210. 

The first protein structures were derived using a technique called isomorphous replacement (IR), developed in the late 1950 s. The materials used are heavy metal derivatives of protein crystals. To obtain a heavy metal derivative of a protein, the protein crystal is soaked in a solution of a heavy metal salt. The metals most used are Pt, Hg, U, lanthanides, Au, Pb, Ag and Ir. The heavy metal or a small molecule containing the heavy metal, depending upon the conditions used, diffuses into the crystal via channels created by the disordered solvent present. The aim is for the heavy metal to interact with some surface atoms on the protein, without altering the protein structure. This is never exactly achieved, but in suitable cases, the changes in structure are slight. 

Unexplained Effects. Some observations are difficult to attribute to any of the freezing mechanisms considered so far. Most amenable to conceptual accommodation are those cases where a particular reactive intermediate, or a particular conformer, appears to have been trapped. This is believed to occur at very low temperatures where mobility at the atomic level is severely limited partly because of little thermal motion and partly because of the physical constraint provided by the glassy or icy structures of the medium. Normally unstable free radical derivatives of proteins can be studied by trapping them at low temperatures (e.g. 79). This technique also can be used to stabilize what appear to be specific conformational isomers of normal structures. For example, this approach has enabled the detection of an ammonia-catalase complex (80), conformers of the iron proteins conalbumin and transferrin (81), and a conformer of the flavoprotein L-amino acid oxidase (82, 83). 

Peptide deformylase is involved in deformylation of the formyl-methionyl derivatives of proteins formed in the prokaryotic translational systems, and thus its inhibitors are searched as candidates for new antibiotic drugs (133). The active peptide deformylase has Fe(ll) ion in the active site, which reacts readily with oxygen. To obtain a stable variant, the Fe(ll) ion is often substituted with Zn(II), although Zn(II)-peptide deformylase has reduced activity by two to three orders of magnitude. Escherichia coli Zn(ll)-peptide deformylase was used as the target enzyme in this study. 

The ultimate precursor of all the carbon atoms in cholesterol and in the other steroids that are derived from cholesterol is the acetyl group of acetyl-GoA. There are many steps in the biosynthesis of steroids. The condensation of three acetyl groups produces mevalonate, which contains six carbons. Decarboxylation of mevalonate produces the five-carbon isoprene unit frequently encountered in the structure of lipids. The involvement of isoprene imits is a key point in the biosynthesis of steroids and of many other compounds that have the generic name terpenes. Vitamins A, E, and K come from reactions involving terpenes that humans cannot carry out. That is why we must consume these vitamins in our diets vitamin D, the remaining lipid-soluble vitamin, is derived from cholesterol (Section 8.8). Isoprene units are involved in the biosynthesis of ubiquinone (coenzyme Q) and of derivatives of proteins and tRNA with specific five-carbon units attached. Isoprene units are often added to proteins to act as anchors when the protein is attached to a membrane. 

The coating products are melted (no solvent hot-melt coating) or dissolved in volatile solvent (usually water) derivatives from cellulose, dextrins, anulsifiers, lipids derivatives of proteins or starch. 

Bis-diazotized benzidine (BDE) will bind to tyrosyl, histidyl, amino, and carboxyl side chain derivates of proteins... 

Amino acid residues are potential targets of free radical oxidation and nitration. Carbonyl derivatives of proteins may be formed by the interaction of protein amino acid side chains, mainly cysteine, histidine, and lysine residues with reactive aldehydes, such as HNE and ONE generated by peroxidation of PUFAs (polyunsaturated fatty acids). Amino acid and peptide biomarkers of oxidative stress are typically focused on specific proteins related to disease pathology. For instance, the oxidation of histidine and methionine are typically discussed in (3-amyloid plaque formation and HNE-derived histidine adducts are the main focus of modifications on low-density lipoprotein (LDL) (An-nangudi et al., 2008). However, there are several specific examples of general biomarkers of oxidative stress that include endogenous histidine containing dipeptides such as carnosine and anserine as well as the very stable o,o -dityrosine. These will be discussed below. 

The y-glutamyl derivatives of protein amino acids so far identified in plants are listed in Table 1. The table gives information on the character of the isolated material and attempts in this manner to give an indication of the reliability of the identification. In many cases no assignment of the configuration of the amino acids has been made but L-configurations are assumed. However, this cannot be taken for granted, especially... 

Table 1. y-Glutamyl Derivatives of Protein Amino Acids Identified in Plants... 

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