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#amino acid properties

3 public questions tagged with this topic.

Plasma Membrane Proteins

Which amino acid property is commonly analyzed in a hydropathy plot to predict transmembrane domains?

Computational prediction of membrane spans relies on physicochemical property hydrophobicity quantifying tendency to partition into non-polar phase. Kyte-Doolittle hydropathy scale derived from experimental water vapor transfer energies assigns isoleucine 4.5, valine 4.2, leucine 3.8, phenylalanine 2.8 as hydrophobic; arginine -4.5, lysine -3.9, asparagine -3.5, aspartate -3.5 as hydrophilic. Sliding window average length nineteen matches bilayer thickness smooths sequence revealing peaks sustained above cutoff indicating candidate transmembrane helices. Complementary scales include Goldman En

Ref: Kyte and Doolittle, Hydropathy Plot for Transmembrane Prediction, J Mol Biol 1982.

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Electrophoresis

Which property causes glutamic acid to move towards anode at pH 7?

Amino acid migration during electrophoresis depends on net charge dictated by relationship between buffer pH and isoelectric point. Glutamic acid possesses acidic side chain with pI approximately 3.22 due to two carboxyl groups. At pH 7, well above pI, both alpha and side-chain carboxyls are deprotonated, conferring net negative charge of minus one to minus two. Anions migrate toward positively charged anode under electric field. Basic pI would imply cationic state and cathodal migration, while molecular weight and solubility do not determine direction. Thus acidic pI explains anodal movement

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Titration of Amino Acids

Which of the following amino acids has the highest pKa value?

Arginine is obtained by applying the relevant formula or quantitative relationship to the given parameters. In Titration of Amino Acids, numerical problem-solving requires understanding the mathematical relationships between biological variables. The calculation involves substituting the provided values into the appropriate equation and solving systematically. The other options (Aspartic acid, Histidine, and Cysteine) result from common calculation errors such as using incorrect formulas, misidentifying variables, inverting ratios, or making arithmetic mistakes.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 3

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