Environmental Engineering Reference
In-Depth Information
Yamashita and Jaffé
2008
). The molecular formula of tryptophan is C
11
H
12
N
2
O
2
and its molecular weight is 204.23. The chemical structure of tryptophan,
C
8
H
5
(NH)-CH
2
(NH
3
)CHCOO
−
, is relatively simple (Fig.
3
q). The fluorophore
at peak T is probably linked to the functional group, -CH
2
-(NH
3
+
)-CH-COO
−
,
while the fluorophore at peak T
uv
is probably connected to the C
8
H
5
(NH)- group
that contains the aromatic ring (Mostofa et al.
2009a
). The resonance configuration
of the functional group, -CH
2
-(NH
3
+
)-CH-COO
−
(Fig.
3
r), may confirm the peak
position of the T-region at longer wavelengths than the T
UV
T-region The fluores-
cence intensity of tryptophan at peak T
uv
is much stronger (two to threefold higher)
than that of peak T. It might be a useful indicator to differentiate the tryptophan-like
component from the protein-like component, which typically shows higher fluores-
cence at the peak T-region than at the peak T
UV
-region (Fig.
3
m, n). Tryptophan
is derived microbially from algae, phytoplankton and bacteria in freshwater,
marine and sediment pore waters (Chen and Bada
1989
; Coble
1996
; Yamashita
and Tanoue
2003a
; Mostofa et al.
2005b
; Determann et al.
1998
; Baek et al.
1988
;
Petersen
1989
; Wu and Tanoue
2001b
; Wu et al.
2001
; Cammack et al.
2004
). Its
very intense fluorescence in aqueous solution could be connected to the functional
group -CH
2
-(NH
3
+
)-CH-COO
−
(Fig.
3
r). Tryptophan is decomposed both pho-
tolytically and microbially in natural waters (Mostofa et al.
2010
,
2007a
; Winter et
al.
2007
; Moran et al.
2000
). The fluorescence Ex/Em wavelength maxima of tryp-
tophan mostly depend on the polarity of the solvent and the type of the protein. The
fluorescence of protein-bound tryptophan is in fact shifted to shorter wavelengths
due to shielding from water (Lakowicz
1983
; Wolfbeis
1985
).
The tyrosine-like component can exhibit two fluorescence peaks at Ex/
Em
=
270-280/293-314 nm in the peak T-region and at 230/304-307 nm in the
peak T
UV
-region (Fig.
3
s; Tables
1
,
2
). The tyrosine-like component has been
detected at Ex/Em
=
270-275/303-314 nm (peak T-region) and at 230/304 nm
(peak T
UV
-region) in a tyrosine standard dissolved in Milli-Q water, and at
275/304 and 230/307 nm when the standard was dissolved in seawater; at
265-280/293-313 nm in rivers and other freshwater systems; at 275/<300 nm in
lakes; at 275/304-306 nm in estuaries; at 270-275/299-332 nm in sea water; at
275/304-306 in soil; at 270/310 nm in water extracted from sugar maple leaves;
at 270/306 nm in drinking water treatment plants; and at 273/309 nm in plant
biomass, animal manure and soil (Fig.
3
s; Tables
1
,
2
) (Coble
1996
; Parlanti et
al.
2000
; Yamashita and Tanoue
2003a
; Mostofa and Sakugawa
2009
; Nakajima
2006
; Provenzano et al.
2004
; Lu and Allen
2002
; Zhang et al.
2009a
; Hunt et al.
2008
; Kowalczuk et al.
2009
; Baghoth et al.
2010
; Chen et al.
2010
; Fellman et
al.
2008
,
2009
,
2010
; Yamashita et al.
2010
,
2011
; Murphy et al.
2008
; Yamashita
and Jaffé
2008
). Tryptophan and tyrosine when present together in peptides (com-
ponent 4) are detected from two peaks at Ex/Em
=
275/306, 338 nm (T-region)
during algal blooming periods, as derived from a mesocom experiment (Table
2
)
(Stedmon and Markager
2005a
). Tyrosine is derived microbially from algal bio-
mass in freshwater and marine environments (Coble
1996
; Yamashita and Tanoue
2003a
; Stedmon and Markager
2005a
; Determann et al.
1998
). Comparison of
tyrosine and trytophan concentrations with their respective fluorescence intensities
+