Chemistry Reference
In-Depth Information
-
-
-
-
-
-
HO
3
PO
-
HO
3
PO
HO
3
PO
OPO
3
H
HO
3
PO
HO
3
PO
HO
3
PO
-
+
H
3
N
SSK
K
CO
2
K
S
G
S
Y
S
G
S
K
G
S
-
OPO
3
H
+
NH
2
N
+
+
H
3
C
CH
3
+
H
NH
2
H
3
C
CH
3
O
CH
3
H
O
NH
+
NH
2
+
NH
2
S = Seryl
H
2
N
O
n=4-9
m=4-9
NH
N
CH
3
K = Lysyl
N
CH
3
m
O
n
NH
+
CH
3
H
G = Glycyl
+
H
CH
3
H
3
C
O
H
3
C
NH
H
Y = Tyrosyl
Figure 24
. A schematic structure of Nat-Sil-1A, after Kröger et al. 2002.
Nakajima and Volcani have not been identified in the highly detailed study performed by
Kröger, Sumper and coworkers. The other form of poststranslational modification involves
the serine residues and these, together with the hydroxyl group on the modified lysine
residues are thought to be phosphorylated (Kröger et al. 2002). The polypeptide has a high
positive charge arising from the number of amino groups but it also has a high negative
charge (each phosphorylated amino acid will contribute one unit of negative charge) such
that the polypeptide will have little overall net charge.
When similar extraction procedures were carried out on a series of other diatoms
from a broad range of species (Kröger et al. 2000) a further class of molecules were
identified whose molecular weights were less than 3.5 kDa and with the exception of
Cylindrotheca fusiformis
, appear to be either one of or the main silaffin type component
of all the other diatoms investigated. Again, electrospray mass spectrometry helped in the
identification of the compounds which were found to be linear polyamines composed of
N-methylaminopropyl or aminopropyl units. An example structure is shown in Figure 25.
The largest number of polyamines was isolated from
Nitzschia angularis
with molecular
weights between 0.6
1.25 kDa (Kröger et al. 2000).
What are the roles for the various extracted biopolymers (sponges and diatoms)?
The formation of silica based materials with specific shape and form requires
manipulation and control of the polymerization process of an amorphous covalently
bonded polymeric material. When the mineral structure of biosilicas is examined by
microscopy (electron and atomic force microscopy) all structures seem to be built up from
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