Water-soluble globular proteins usually have an interior composed almost entirely of non polar, hydrophobic amino acids such as phenylalanine, tryptophan, valine and leucine witl polar and charged amino acids such as lysine and arginine located on the surface of thi molecule. This packing of hydrophobic residues is a consequence of the hydrophobic effeci which is the most important factor that contributes to protein stability. The molecula basis for the hydrophobic effect continues to be the subject of some debate but is general considered to be entropic in origin. Moreover, it is the entropy change of the solvent that i  [c.531]

Some ammo acids have side chains that bear acidic or basic groups As Table 27 3 indicates these ammo acids are characterized by three values The third pK reflects the nature of the side chain Acidic ammo acids (aspartic and glutamic acid) have acidic side chains basic ammo acids (lysine arginine and histidine) have basic side chains The isoelectric points of the ammo acids m Table 27 3 are midway between the pK values of the zwitterion and its conjugate acid Take two examples aspartic acid and lysine Aspartic acid has an acidic side chain and a pi of 2 77 Lysine has a basic side chain and a pi of 9 74  [c.1118]

The pi of lysine is the average of pK 2 (8 95) and the pK of the side chain (10 53) or 9 74  [c.1118]

Thus if a mixture containing alanine aspartic acid and lysine is subjected to electrophoresis m a buffer that matches the isoelectric point of alanine (pH 6 0) aspartic acid (pi = 2 8) migrates toward the positive electrode alanine remains at the origin and lysine (pi =9 7) migrates toward the negative elec trode (Figure 27 3b)  [c.1120]

FIGURE 27 3 Application of electrophoresis to the separation of aspartic acid alanine and lysine according to their charge type at a pH corresponding to the isoelectric point (pi) of alanine  [c.1120]

Lysine reacts with two equivalents of benzyloxycarbonyl chio ride to give a derivative containing two benzyloxycarbonyl groups What is the structure of this compound /  [c.1137]

For a 3 cm long molecule of DNA to fit inside a cell so tiny that we can only see it with a microscope the polynucleotide chain must be folded into a more compact form Not only must the DNA be compacted it must be folded m a way that allows it to carry out its mam functions The way the chain is folded defines the tertiary structure of a nucleic acid The compacting mechanism is a marvel of cellular engineering A twisted tangle of indefinite shape would present serious problems as a vessel for storing genetic information Coiling the duplex however reduces its length without blocking access to important parts of its structure Remember though that DNA is negatively charged at biological pH Thus the tighter the coil the closer together are the negatively charged phosphate units and the less stable the coil Nature solves this puzzle for chromosomes by wrapping short sections of the DNA around proteins called histones (Figure 28 6) Histones are a family of five proteins rich m basic ammo acids such as arginine and lysine which are positively charged at biological pH The positively charged histones stabilize the coiled form of the negatively charged DNA The species formed between a section of DNA and histones is called a nucleosome Each nucleosome contains about one and three quarters turns of coil comprising 146 base pairs of DNA and is separated from the next nucleosome by a linker of about 50 base pairs of DNA Figure 28 7 shows a molecular model of a single nucleosome  [c.1171]

Trypsin (Section 27 10) A digestive enzyme that catalyzes the hydrolysis of proteins Trypsin selectively catalyzes the cleavage of the peptide bond between the carboxyl group of lysine or arginine and some other amino acid  [c.1296]

Lysine, methyl ester (/it = 0.1) 6.965(+l) 10.251(0)  [c.882]

L-Lysyl-L-lysyl-L-lysine (/r- = 0.1) 3.08(+2) 7.34(+l) 9.80(0) 10.54(-1)  [c.883]

L-Lysyl-D-lysyl-L-lysine (/r- = 0.1) 2.91(+2) 7.29(+l) 9.79(0) 10.54(-1)  [c.883]

L-Lysyl-D-lysyl-lysine (/r- = 0.1) 2.94(+2) 7.15(+1) 9.60(0) 10.38(-1)  [c.883]

Derived from Lysine [ALKALOIDS] (Voll)  [c.27]

H02CC(H)(NH2)(CH2)3C(H)(NH2)C02H. M.p. at least 305"C. The o, l and meso forms are all isolated from hydrolysates of bacterial proteins. It is an intermediate in the biosynthesis of lysine in many bacteria.  [c.131]

H2N-CH2 [CH2j3.CH(NH2) COOH. Colourless needles, m.p. 224 C (decomp.), very soluble in water, insoluble in alcohol. L-(-H)-Lysine is one of the basic amino-acids occurring in particularly large quantities in the protamine and histone classes of proteins. It is an essential amino-acid, which cannot be synthesized by the body and must be present in the food for proper growth. It can be manufactured by various fermentation processes or by synthesis.  [c.244]

Protein monolayers tend to be expanded relative to those at the air-water interface [94]. Davies [95] studied hemoglobin, serum albumin, gliadin, and synthetic polypeptide polymers at the water-petroleum ether interface with the view of determining the behavior of the biologically important e-NH2 groups and concluded that on compression they were forced into the oil phase. Neumann and co-workers found that interfacial pressures were higher for human albumin (HA) at the HA solution-decane interface than at the solution-air interface [96]. Hermel and Miller investigated the effect of the secondary structure of poly-L-lysine on its adsorption at the solution-dodecane interface [97]. They found that the a-helix occupies a smaller area per residue and yields a greater  [c.551]

A likely exit path for the xenon was identified as follows. Different members of our research group placed the exit path in the same location and were able to control extraction of the xenon atom with the tug feature of the steered dynamics system without causing exaggerated perturbations of the structure. The exit path is located between the side chains of leucines 84 and 118 and of valine 87 the flexible side chain of lysine 83 lies just outside the exit and part of the time is an obstacle to a linear extraction (Fig. 1).  [c.142]

The comparison of both data sources qualitatively shows a similar picture. Regions of high mobflity are located especially between the secondary structure elements, which are marked on the abscissa of the plot in Figure 7-17. Please remember that the fluctuations plotted in this example also include the amino acid side chains, not only the protein backbone. This is the reason why the side chains of large and flexible amino acids like lysine or arginine can increase the fluctuations dramatically, although the corresponding backbone remains almost immobile. In these cases, it is useful to analyze the fluctuations of the protein backbone and side chains individually.  [c.373]

IS placed at the center of a sheet of cellulose acetate The sheet is soaked with an aqueous solution buffered at a pH of 6 0 At this pH aspartic acid C ) exists as its — 1 ion alanine as its zwittenon and lysine as its +1 ion  [c.1120]

The enzymes that catalyze the hydrolysis of peptides are called peptidases, proteases, or proteolytic enzymes Trypsin a digestive enzyme present m the intestine catalyzes only the hydrolysis of peptide bonds involving the carboxyl group of a lysine or arginine residue Chymotrypsin another digestive enzyme is selective for peptide bonds involving the carboxyl group of ammo acids with aromatic side chains (phenyl alanine tryrosme tryptophan) One group of pancreatic enzymes known as car boxy peptidases catalyzes only the hydrolysis of the peptide bond to the C terminal ammo acid In addition to these many other digestive enzymes are known and then-selectivity exploited m the selective hydrolysis of peptides  [c.1130]

Many pharmaceutical compounds are weak acids or bases that can be analyzed by an aqueous or nonaqueous acid-base titration examples include salicylic acid, phenobarbital, caffeine, and sulfanilamide. Amino acids and proteins can be analyzed in glacial acetic acid, using HCIO4 as the titrant. For example, a procedure for determining the amount of nutritionally available protein has been developed that is based on an acid-base titration of lysine residues.  [c.303]

See pages that mention the term Lysine : [c.28]    [c.74]    [c.188]    [c.188]    [c.244]    [c.244]    [c.267]    [c.408]    [c.432]    [c.2697]    [c.439]    [c.229]    [c.1112]    [c.1114]    [c.1115]    [c.1118]    [c.1119]    [c.1120]    [c.882]    [c.882]    [c.883]    [c.1179]    [c.735]    [c.20]    [c.146]    [c.581]    [c.581]   
Introduction to protein structure (1999) -- [ c.0 ]

Thin-layer chromatography Reagents and detection methods (1990) -- [ c.435 ]