Biology Reference
In-Depth Information
The mean
k
and
K
values of 20 determinations for DV and MV Chl(ide)
a
amounted
to k
1
¼
0.3675
0.0066;
k
2
¼
18.3010
0.8119;
k3
¼
0.0548
0.9799. By substitution
for the values of
k
1
,k
4
,K
1
and
K
2
in Eqs. (
3.64
) and (
3.65
) and by further reduction
of the substituted equations, the latter assume the form:
0.0025; k
4
¼
2.7220
0.0516;
K
1
¼
0.9799;
K
2
¼
ð
Þ
a
ð
Þ¼
:
ð
Þ
:
ð
Þ
(3.67)
DV Chl
ide
E458 F674
1
0205
E458 F674
0
0557
E447 F674
and
MV Chl
ð
ide
Þ
a
ð
E447 F674
Þ¼
1
:
0205
ð
E447 F674
Þ
0
:
3749
ð
E458 F674
Þ
(3.68)
3.7.3 Conversion of the DV and MV Chlorophyll(ide)
a Soret Excitation Ratios to DV and MV
Chlorophyll(ide) a Concentrations
As was pointed out in Sect.
3.5.2.4
, the ratio of the net Soret excitation amplitudes
must be converted to an authentic concentration ratio before actual MV and DV
amounts can be calculated (Tripathy and Rebeiz
1985
). This is achieved by
reference to a standard calibration curve. For MV and DV Chl(ide)
a,
such a
calibration curve can be constructed as follows:
(a) by mixing authentic MV and DV Chl(ide)
a
in known proportions,
(b) by recording the required77
K spectra on every mixture,
(c) by calculating the ratio of the net MV to the net DV Soret excitation amplitudes
for every mixture, with the help of Eqs. (
3.67
) and (
3.68
), and finally
(d) by plotting the authentic MV/DV Chl(ide)
a
ratios, on the abscissa for example,
against the experimental MV/DV ratio of the net Soret excitation amplitudes on
the ordinate.
Under our instrumental conditions, for experimental Soret excitation ratios equal
to or smaller than 2.5 such a plot yielded a straight line with an intercept of 0.3150,
a slope of 0.5405, and a correlation coefficient of 0.9958. At experimental Soret
excitation ratios larger than 2.5, the curve exhibited an ordinate intercept of 0.4248,
a slope of 0.4675, and a correlation coefficient of 0.9971. The concentration of MV
and DV Chl(ide)
a
in the mixture was then calculated from the total amount of
MV + DV Chl(ide)
a
and from the slopes and intercepts of the calibration curve as
illustrated below. The reliability of Eqs. (
3.67
) and (
3.68
) in determining the
proportions of MV and DV Chl(ide)
a
in mixtures of the two tetrapyrroles
amounted to
0.27
2.69 and 2.69
5.95 %, respectively (Table
3.10
).
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