Lysin amino acid

Figure 5.9 Models of hexo-kinase in space-filling and wireframe formats, showing the cleft that contains the active site where substrate binding and reaction catalysis occur. At the bottom is an X-ray crystal structure of the enzyme active site, showing the positions of both glucose and ADP as well as a lysine amino acid that acts as a base to deprotonate glucose.

Experimental results regarding the role of the histone tails indicate that these histone domains play a critical role in chromatin folding [358,365]. Removal as well as the modification (acetylation) of the lysine amino acids within these regions produces an imbalance of the electrostatic interactions, which results in a hierarchically impaired folding ability (H3/H4-H2A/H2B>H3/H4>H2A/H2B) of the chromatin fiber [358,366-369]. Therefore, sources of histone tail variability (histone variants and post-translational modifications other than lysine acetylation) are also likely to alter the extent of folding of chromatin. 

Enzymes are very sophisticated systems that apply sound chemical principles. The side-chains of various amino acids are used to supply the necessary bases and acids to help catalyse the reaction (see Section 13.4). Thus, the enzyme aldolase binds the dihydroxyacetone phosphate substrate by reacting the ketone group with an amine, part of a lysine amino acid residue. This forms an imine that becomes protonated under normal physiological conditions. 

For molecules of similar size, the magnitude of the electrophoretic mobility increases with charge. A protein charge ladder is a synthetic mixture made from a single protein with many different charges. For example, we can obtain such a mixture by acetylating variable numbers of lysine amino acid side chains (Table 10-1) to reduce their charge from 1 (R—NH f) to 0 (R-NHC(=0)CH3).26... 

Barley protein, moisture, lysine, amino acid, (i-glucan... 

GS, and MDH were increased by HEf treatment of 1.79,1.50, and 1.49-fold, respectively. As a consequence of the increased activity of these enzymes, an increase in the amount of methionine, threonine, isoleucine, and lysine, amino acids derived from the oxalacetate pathway, were found. 

Retinol is attached to the lysine amino acid at position 296 in this unrolled representation. The seven individual helices shown completely surround the retinoid and isolate it from the exterior environment. This is more clearly represented in Figure 5.1.1-2 from Dratz Hargrave17. It shows the retinol ligand completely enclosed by the individual helices... 

The reverse aldol reaction is catalyzed by an enzyme called aldolase. One of the roles of the enzyme is to stabilize the enolate anion intermediate because such ions are too basic to be produced under physiological conditions. In animals, aldolase accomplishes this task by forming an inline bond between the carbonyl group of fructose-1,6-bisphosphate and the amino group of a lysine amino acid of the enzyme. As a result, the product of the reverse aldol step is an enamine derived from DHAP rather than its enolate anion. (Section 20.8 shows that enamines are the synthetic equivalents of enolate anions.) The formation of the strongly basic enolate anion is avoided. This process is outlined here ... 

There are pyridine cross-links between the parallel chains of collagen of bone mass, namely, between the lysine amino acid residues (PYD), and between the lysine and hydroxylysine residues (DPD). They are found in nonhelical terminal (N- and C-terminal) regions of collagen macromolecules—telopeptides. They are the final products of the biodegradation of collagen excreted to urine in the kidneys. 

Figure 15-11. Structures of four (arginine, histidine, glutamic acid, and lysine) amino acids.

The involvement of lysine amino acid residues on cytochrome c in the heterogeneous reactions with functionalized electrodes seems to have been established. Importantly, it is now thought that the proposed protein-promoter complex is more likely to be dynamic, as revealed by the results of a recent investigation (28) of site-specific 4-chloro-3,5-dinitrophenyl (CDNP)-substituted cytochrome c. It was found that monosubstitution of either Lys 13 or Lys 72 did not result in any significant change in its electrochemical response, whereas two modifications greatly decreased the heterogeneous rate constant, and complete loss of electrochemical activity was observed upon modification of more lysines. It was proposed that the electrode reaction occurred in numerous rotational conformations. Therefore, for the mono-... 

About half of rhodopsln s mass forms seven a-hellces, which are embedded In the lipid bllayer of rod disks. The remaining polypeptide chains extend Into the aqueous environment of the cytoplasm or the disk Interior, linking the helices. Retinal Is bound as a protonated Schiff base to a lysine amino acid residue In the carboxyl terminal helix. The chromophore is held In a pocket that is nearly parallel to the membrane surface. When light strikes rhodopsln, the 11-cis double bond of the protein-bound retinal Isomerlzes to the trans form, which leads to the separation from the protein opsin. To complete the visual cycle, the all-transretlnal slowly Isomerlzes back to the 11-cis Isomer, which recombines with opsin to reform rhodopsln. However, little Is known about how the Isomerization of retinal In rhodopsln triggers the transduction process (72,73) ... 

A.25.2 At the blood pH, the lysine amino acid groups are ionized and the exposed surface will be more positive. This will change the zeta potential at the blood-vessel interface and may even switch the sign of the zeta potential. 

I he standard analytical construct used for library production in Diversity Sciences at GlaxoSmithKline is shown in Figure 8.1. The analytical construct uses the common Knorr acid cleavable linkers at the first and second linker positions. The terminal linker is photocleavable and is released upon exposure to 350-nM light [12-15]. The construct contains the mass-code block and uses isotopically labeled Gly as a peak splitting element to facilitate compound identification by mass spectrometry. Also, the construct has two lysine amino acid groups to aid the ionization process of both the code block and the ligand... 

Covalent attachment (e.g., through bioconjugate chemistry) between free amino groups of enzyme, particularly for lysine amino acid residues, and charged groups on the immobilization matrix... 

Figure 14.1 shows the plot of the MLR-calculated electrophoretic mobility against the experimental values for the validation and test sets. This plot showed an improved correlation of P = 0.895 in the predictive ability of the model over the use of the simple Offord relationship (r = 0.878). ffowever, some MLR-calculated electrophoretic mobilities showed a large deviation from the experimental values (9). The MLR model overestimated the electrophoretic mobility of peptides containing arginine (R), histidine (H), and lysine amino acids. These amino acids contribute a charge -f1 to the peptide. Jalali-... 

Salt Bridge Between an Aspartic Acid Side-Chain at One Position in a Protein Molecule and a Lysine Amino Acid Side-Chain in Another Position... 

Scheme 19.17 Nucleophilic opening of penicillin s beta-lactam. This process occurs under basic conditions and is driven by the energetics associated with relieving the considerable bond-angle strain present in the 4-membered-ring. Two pathways are shown (i) The top results in acylation of a biological surface that has a good nucleophile such as the terminal amino-group on a lysine amino acid residue and, (ii) The lower represents a ready hydrolytic ring-opening by a water molecule to produce an inactive degradation product called penicilloic acid.

An individual collagen polypeptide chain has a large number of repeating amino acid sequences, most often glycine-X-Y, where X is often proline and Y is often hydroxyproline. Lysine, in its pure form or modified to hydroxylysine, is also found in collagen. Both hydroxyproline and hydrox-ylysine are formed via the enzyme-catalyzed oxidations of the profine and lysine amino acid side chains, which occur after the collagen polypeptide has been synthesized. These enzymatic reactions reqtiire ascorbic acid (vitamin C) as a cofactor. 

Fig. 2 Hapten/peptide and p-i concept of T cell stimulations by drugs, (a) Haptens haptens are chemically reactive compounds. Drugs like penicillin are haptens they bind to lysine amino acids in proteins or by the SH-group formed by opening the thiazolidine ring. This covalent binding can modify soluble or cell bound molecules. They can even bind directly to the immunogenic major histocompatibiliy complex (MHC)/peptide complex on antigen presenting cells (ARC), either to the embedded peptide or to the MHC molecule itself. Thus, the chemical reactivity of haptens can lead to...

Figure 31.18 (a) HRSEM micrographs of graphene laminates modified with urea and (b) with L-lysine amino acid. 

When estimating the pi for arginine, aspartic acid, glutamic acid, histidine, and lysine (amino acids that contain either two carboxyl or two ammonium groups), we use the p s of the two groups that are closest in value. For example, the pi of lysine would be determined as follows ... 

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