Valine

Val · V · 117.15 Da

Essential Essential

Isopropyl

Branched at the β-carbon, which crowds the backbone and favors β-sheets. Glu→Val at position 6 of β-globin causes sickle cell disease.

Mnemonic

V for Valine, the V-shaped fork of two methyls on Cβ.

Ionization ladder

pKa	Group	Change	Charge
2.32	α-carboxyl	-COOH → -COO⁻	0 → −1
9.62	α-amino	-NH₃⁺ → -NH₂	+1 → 0

pI = (2.32 + 9.62) / 2 = 5.97, the midpoint of the two pKa values that bracket the neutral species.

Net charge across pH

pH 1+1

pH 40

pH 70

pH 10−1

pH 13−1

A group is deprotonated once the pH climbs past its pKa. Add the contributions and you have the net charge, with no memorization required.