What is the pl (isoelectric point) of the protein you chose in the previous prob

Question

What is the pl (isoelectric point) of the protein you chose in the previous problem? What is the pl of the peptide MEHR? You may find ExPASy's pl/MW calculation server (http://web.expasy.org/compute pi/) to be useful in calculating the pl of your protein, however, for the peptide, please calculate the pl by hand and show your work: you may use the pKa values on Wikipedia https://en.wikipedia.org/wiki/Proteinogenic amino acid# Chemical properties. you may need to copy and paste this link into your browser as ctrl-clicking it may not work) for your calculations- as always with this sort of thing, please cite which tools/tabulations you use. (5 pts)

Explanation / Answer

Isolectric point is that where positive and negative charge are equal.

MEHR

In this peptide

Pka value of N-terminal of methionine is= 9.28

Pka value of aspartic acid (E) =4.25

Pka value of histidine (H)= 6.54

Pka value of Arginine (R) =12.3

-COOH terminal Arginien R= 1.82

There are several alogrtyms has been developed where only side chains have been taken but in some case free N-teminal and C-terminal residues also considered.

First by taking side chains 4.25+6.54+12.4)/3= 7.73

Considering terminal amino and carboxylit groups

(9.28+4.25+6.54+12.3+1.82)/5=6.73

Various values of Pka is taken from: https://en.wikipedia.org/wiki/Proteinogenic_amino_acid

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