Biomedical Engineering Reference
In-Depth Information
that the majority of their hydrophobic amino acid residues are buried internally in the molecule
and, hence, are shielded from the surrounding aqueous environment (Chapter 2). Internalized
hydrophobic groups normally associate with adjacent hydrophobic groups. A minority of hy-
drophobic amino acids, however, are present on the protein surface and, hence, are exposed to
the outer aqueous environment. Different protein molecules differ in the number and types of
hydrophobic amino acid on their surface, and hence on their degree of surface hydrophobicity.
Hydrophobic amino acids tend to be arranged in clusters or patches on the protein surface. Hy-
drophobic interaction chromatography fractionates proteins by exploiting their differing degrees
of surface hydrophobicity. It depends on the occurrence of hydrophobic interactions between
the hydrophobic patches on the protein surface and hydrophobic groups covalently attached to
a sui table matrix.
The most popular hydrophobic interaction chromatographic beads (resins) are cross-linked aga-
rose gels to which hydrophobic groups have been covalently linked. Specifi c examples include
ALANINE
VALINE
LEUCINE
ISOLEUCINE
COO -
COO -
COO -
COO -
α
α
α
α
H 3 N +
H 3 N +
H 3 N +
H 3 N +
C
H
C
H
C
H
C
H
CH 3
CH
CH 2
CH 3
CH 3
CH 2
CH 3
CH 3
CH
CH 3
CH 3
CH 3
TRYPTOPHAN
METHIONINE
PHENYLALANINE
PROLINE
COO -
COO -
COO -
COO -
H
H
H
α
C
α
α
α
H 3 N +
H 3 N +
C
H
H 3 N +
C
H
C
H
N +
C
H
H
C
C
CH 2
CH 2
CH 2
H
H
H
H
H
H
CH 2
C
C
H
CH
C
C
C
C
S
NH
H
C
C
C
C
C
H
H
CH 3
C
C
H
H
H
Figure 6.12 Structural formulae of the eight commonly occurring amino acids that display hydrophobic
characteristics
Search WWH ::




Custom Search