Amino smallest

The reaction center is built up from four polypeptide chains, three of which are called L, M, and H because they were thought to have light, medium, and heavy molecular masses as deduced from their electrophoretic mobility on SDS-PAGE. Subsequent amino acid sequence determinations showed, however, that the H chain is in fact the smallest with 258 amino acids, followed by the L chain with 273 amino acids. The M chain is the largest polypeptide with 323 amino acids. This discrepancy between apparent relative masses and real molecular weights illustrates the uncertainty in deducing molecular masses of membrane-bound proteins from their mobility in electrophoretic gels. 

Very few self-sufficient viruses have only 60 protein chains in their shells. The satellite viruses do not themselves encode all of the functions required for their replication and are therefore not self-sufficient. The first satellite virus to be discovered, satellite tobacco necrosis virus, which is also one of the smallest known with a diameter of 180 A, has a protein shell of 60 subunits. This virus cannot replicate on its own inside a tobacco cell but needs a helper virus, tobacco necrosis virus, to supply the functions it does not encode. The RNA genome of the satellite virus has only 1120 nucleotides, which code for the viral coat protein of 195 amino acids but no other protein. With this minimal genome the satellite viruses are obligate parasites of the viruses that parasitize cells. 

The proteins in food supplements are often hydrolyzed to short peptides to make them easier to absorb. A high content of amino acids is deleterious, however. Thus, there is ongoing interest in determining the size distribution of peptides in protein hydrolyzates. Silvestre et al. (29,30) used a PolyHEA column to compare casein hydrolyzates prepared through various methods. They were able to assess the content of the smallest peptides, as well as amino acids (Fig. 8.13). 

Amino acids with polar but nonionized side chains Among amino acids with polar side chains, serine is the smallest it is not much larger than alanine. With a —CH2OH side chain, serine participates well in hydrogen bonding and often occurs in regions of a peptide that ar e exposed to water. 

The amino acid compositions and sequences of the /3-strands in porin proteins are novel. Polar and nonpolar residues alternate along the /3-strands, with polar residues facing the central pore or cavity of the barrel and nonpolar residues facing out from the barrel where they can interact with the hydrophobic lipid milieu of the membrane. The smallest diameter of the porin channel is about 5 A. Thus, a maltodextrin polymer (composed of two or more glucose units) must pass through the porin in an extended conformation (like a spaghetti strand). 

Transfer RNA (tRNA) serves as a carrier of amino acid residues for protein synthesis. Transfer RNA molecules also fold into a characteristic secondary structure (marginal figure). The amino acid is attached as an aminoacyl ester to the 3 -terminus of the tRNA. Aminoacyl-tRNAs are the substrates for protein biosynthesis. The tRNAs are the smallest RNAs (size range—23 to 30 kD) and contain 73 to 94 residues, a substantial number of which are methylated or otherwise unusually modified. Transfer RNA derives its name from its role as the carrier of amino acids during the process of protein synthesis (see Chapters 32 and 33). Each of the 20 amino acids of proteins has at least one unique tRNA species dedicated to chauffeuring its delivery to ribosomes for insertion into growing polypeptide chains, and some amino acids are served by several tRNAs. For example, five different tRNAs act in the transfer of leucine into... 

Not only the smallest optically active amino acid (alanine), but also leucine, several (substituted) aromatic amino acids, heterosubstituted amino acids (methionine, homomethionine and thienylglydne) and even an iminoacid, proline, are obtainable in both the L- and D-form. 

Other fibrous proteins contain extensive regions of pleated sheets. The fibers spun by a silkworm, for example, are made almost entirely of fibroin, a protein composed primarily of just three amino acids glycine (45%), alanine (30%), and serine (12%). Each chain of fibroin contains extensive regions where a sequence of six amino acids occurs repeatedly . .. -Gly-Ser-Gly-Ala-Gly-Ala-. .. Notice that every other amino acid is glycine, which is the smallest amino acid. This alternating arrangement is an important feature in the packing of the strands that make up the pleated sheet. 

C13-0087. The smallest proteins contain about 50 amino acids. How many different proteins containing 50 amino acids can be formed from the 20 common amino acids Express your answer in power of 10 notation. 

The analysis of extraterrestrial matter is concentrated on the detection of nucleic acid and protein building blocks, i.e., N-heterocycles and amino acids. The search for such compounds began immediately after the fall of the Murchison meteorite. Twenty-two amino acids were detected in it as early as 1974 eight of them pro-teinogenic, ten which hardly ever occurred in biological material, and four which were unknown in the biosphere. Up to now, about 70 amino acids have been identified (Cronin, 1998), the most common being glycine and a-aminoisobutyric acid. The latter is a branched-chain amino acid with the smallest possible number of carbon atoms. The most frequently found amino acids occur in concentrations of... 

Hardness data for only two amino acids were found in the literature. They are glycine and alanine. They are the smallest of the amino acids. Both consist of rather flat tablet-like collections of atoms that form layered crystal structures in which the molecular sub-groups within the layers are held together by hydrogen bonds (Albrecht and Corey, 1939), and the molecules by London forces. Their hardnesses are ... 

The more compact nature of each a chain explains why we find so few different amino acids present in the primary structure. Glycine has the smallest side chain group of the amino acids, just a single hydrogen atom, as anything more bulky would prevent the tight coiling required to achieve the three residues per turn. 

In this approach, the size of the protein is taken into consideration. The size of the protein depends on the number of amino acids it contains. This property can be used in protein purification. The column material consists of a porous matrix for proteins to diffuse Into (Fig. A.3). The smaller proteins get entangled Inside the porous material and hence their mobility Is restricted. In contrast, the larger proteins do not get entangled and could just pass through. Hence, In the elution profile, the larger molecules would be the first ones to elute, while the smallest ones will be last to elute. 

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