Geology Reference
In-Depth Information
others (1990; Sokolov et al. 2001). Proton dis-
sociation from cell surface ligands can be described
by the following equation:
sites and m additions of titrant is:
K
a
i
K
a
i
þ [H
þ
]
j
a
ij
¼
(5)
HL
0
,H
þ
þ L
(1)
The n 1 vector contains the ligand concen-
trations for each of the m sites and the m 1
vector b contains the measured charge excess
C
Bj
C
Aj
þ [H
þ
]
j
[OH
]
j
.
where L
2
is the deprotonated binding site with a
negative charge and H
þ
is a proton in solution,
whose activity in the bulk solution was measured
with a pH electrode. The concentration of proto-
nated and deprotonated surface sites can be quanti-
fied with the corresponding mass action equation:
Infrared spectroscopy
Pellets for infrared analysis were obtained by care-
fully grinding a mixture of 1-2 mg of polymeric
substancies with 300 mg of dry KBr and then press-
ing them into in a 16-mm diameter mold. The pellet
technique was used because most bacterial poly-
mers were poor water-soluble and films could not
be prepared. Fourier transform infrared spec-
troscopy (FTIR) spectra were recorded on a Perkin
Elmer instrument SPECTRUM (PE-IR) with a res-
olution of 1 cm
21
. Spectra were run in the region
400-4500 cm
21
. No smoothing was performed.
K
a
¼
[H
þ
][L
]
[HL
0
]
(2)
where K
a
is the dissolution constant for HL
0
.
The useful transformation of the acid base raw
data for the j'th addition of acid or base is the
charge balance expression (Brassard et al. 1990):
b
meas, j
¼ C
Bj
C
Aj
þ [H
þ
]
j
[OH
]
j
(3)
Calcium carbonate precipitation
experiments on agarose beads
where C
Bj
and C
Aj
correspond to concentrations of
base and acid for the j'th addition of titrant, [H
þ
]
j
and [OH
2
]
j
are obtained from the measured
proton concentration. As described previously, the
charge excess b
meas,i
can be calculated as a function
of measured [H
þ
] and adjustable (K
a
and L
T
)
speciation parameters (Martinez et al. 2002) as:
Agarose beads were prepared by modified method
which is described in details in Strathmann et al.
(2000). Briefly, two solutions were prepared: for
the first solution 8 mL of Span85 was added into
200 mL of 60 8C cyclohexane. For the second sol-
ution, agarose powder was added to 98 8C nanopure
water (1-5%, w/v) under constant stirring. When
completely dissolved, the agarose solution was
cooled down to 60 8C and then emulsified in the
cyclohexane/Span85 solution (60 8C) at a stirring
speed of 500 min
21
. After 10 minutes of stirring
the water/oil emulsion was cooled down to 20 8C
without stirring. The supernatant was decanted and
the remaining beads washed 4 times with nanopure
water. The beads can be stored in 50 mL Eppendorf
tubes at 280 8C.
þ S
b
calc, j
¼
X
n
K
a
i
L
T
i
K
a
i
þ [H
þ
]
j
(4)
i¼1
where S is a constant term analogous to the acid neu-
tralizing capacity or the initial protonation state of
the surface (Brassard et al. 1990; Cernik et al.
1995). The surface sites are considered as a sum
of n monoprotonic ligands [L
2
] with dissociation
constants K
ai
and total concentrations L
T
i
. In prac-
tice, S allows a modeling positive charge on the
surface.
Equation (3) could be solved by fixing the pK
a
values as a grid from a minimum to maximum
value at fixed step sizes (Cox et al. 1999). The
ligand concentration associated with each pK
a
value is assigned a positive value where zero is a
possible result; the result is the so-called pK
a
spec-
trum. The pK
a
spectrum approach is used here to
determine the best fit of K
ai
/L
T
i
pairs, with pK
a
values fixed as a grid from 4 to 10 at fixed step
sizes (0.2). Once the pK
a
values are selected, the
matrix version of equation (3) is set up as Ax ¼ b.
The entry a
ij
in the m n matrix A for n proposed
Calcium carbonate precipitation experiments
After slowly defrosting the 12 mL Eppendorf-tubes
containing the polysaccharides samples, a spatula
tip of agarose beads was added to each sample.
Then 37% formaldehyde was added to make 4%
solution and the tubes were stored horizontally for
3 hours at room temperature to allow the polysac-
charides to attach onto the beads. Finally agarose
beads with attached polysaccharides were washed
with phosphate buffer. Subsequently, beads were
transferred into the prepared and labelled vials
which contained 1-2 mL of the mixture containing
Search WWH ::
Custom Search