Chemistry Reference
In-Depth Information
Plasmodium falciparum
Causative agent of malaria.
platelet
Non-nucleated blood cell involved in primary hemostasis.
polysialic acid (PSA or polySia)
A linear homopolymer of variable length of 50 or more sialic residues, joined by
α
2,9 linkages. It is found in mammalian tissues of neuroectodermal and
mesodermal origin, most commonly known when attached to two
N
- glycans in
the fi fth immunoglobulin-like domain of the neural cell adhesion molecule. Its
presence in bacteria, e.g., as capsular polysaccharide (colominic acid) in
Escherichia
coli
and in
Neisseria meningitidis
, when presenting lactones or de-
N
- acetylated sites,
makes it a tool for vaccination. Further substitutions by sulfation are known from
sea urchin (here fl agellasialin). Please note: when men are concerned about PSA,
they mean prostate- specifi c antigen, for lectinologists it can mean
Pisum sativum
agglutinin.
2,8 or
α
polyvalency
Clustering of (carbohydrate) epitopes that can raise binding affi nity to neighboring
partners by orders of magnitude (
see also
glycoside cluster effect and
multivalency).
prepropeptide
A biosynthetic precursor of a peptide typically containing three domains: an N-
terminal signal sequence, a domain that is removed during processing (the pro-
domain), and the domain containing what will become the mature peptide.
protegrin
A family of unusually potent antimicrobial peptides originally isolated from
porcine leukocytes. Protegrins contain 16-18 amino acid residues and have a
β
-hairpin structure stabilized by two intramolecular disulfi de bridges.
protein body
Storage organelle formed from the central vacuole of a plant cell during its devel-
opment. Protein bodies are lined by a single membrane and contain the typical
storage proteins, lectins, several hydrolases and
myo
- inositolhexaphosphates
(phytin). They are also called storage vacuoles.
protein domain
Many proteins, including lectins, contain more than one component protein
module, called a domain. A domain has a compact three- dimensional structure,
which may fold independently of the rest of the protein, and may function and
evolve semi-independently. The sequence of a protein domain is typically 100- 200
amino acids long.
