Biomedical Engineering Reference
In-Depth Information
The.rate.enhancements.achieved.with.artiicial.ribozymes.are.comparable.with.the.ones.
observed.with.abzymes,.with.maximum.values.of.up.to.10
−10
.s
−1
.(Suga.et.al..1998)..However,.
although.artiicial.ribozymes.cannot.compete.with.protein.enzymes,.they.are.able.to.out-
perform.their.natural.counterparts.(Silverman.2009).
3.9 Other Nonprotein Artificial Enzymes
Although.nature.has.chosen.to.build.its.nanomachines.out.of.protein.and.nucleic.acids,.other.
types.of.polymers.are.also.capable.of.protein-like.three-dimensional.folds.and.functions..
Alternative. backbones. and. side. chains. (Figure. 3.6). may. prove. to. have. advantages. over.
proteins.in.future.applications..Research.on.these.types.of.biomimetic.folding.polymers,.
known.as.foldamers,.is.progressing.rapidly.
Nature. has. elected. to. use. only. l-amino. acids. at. the. expense. of. their. mirror-image.
enantiomers,. the. d-amino. acids.. In. principle,. for. each. natural. protein,. a. corresponding.
sequence. of. d-amino. acids. will. fold. into. a. mirror-image. protein. with. activity. against.
R
1
R
3
H
O
H
N
N
N
N
O
H
O
R
2
H
(a)
R
1
O
R
3
H
H
N
N
N
N
O
H
O
H
R
2
(b)
R
2
R
4
O
N
N
N
N
R
1
O
R
3
O
(c)
R
1
O
R
2
O
R
3
N
N
N
H
(d)
O
O
N
N
N
H
R
1
R
2
(e)
Figure 3.6
Comparison. of. the. chemical. backbones. of. various. foldamers.. (a). l-peptide,. (b). d-peptide,. (c). peptoid,.
(d).β
2
-peptide,.and.(e).β
3
-peptide.
