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sine phosphate and show contributions from all constituents of this nucleotide
(adenine, ribose and phosphate; see band assignments in Fig. 4.7 [86]). A
comparison with data of pure adenosine monophosphate (AMP) and adeno-
sine triphosphate (ATP) suggested a prevailing contribution from AMP, since
triphosphate and diphosphate markers were absent. From this 'AMP/ATP
fingerprint' we concluded that one can detect molecular species involved in
the generation of a specific endosomal milieu: The key players in the acidi-
fication and pH regulation of endosomes include an ATP-dependent proton
pump and a Na-K-ATPase [87, 88]. Furthermore, the endosome acidification
profile can be modified by cyclic AMP [89].
Fig. 4.7.
SERS spectrum collected from endosomes in the cell line J774 after
incubation with gold nanoparticles. It was identified as SERS spectrum of AMP
and/or ATP. Band assignments are based on [86] are indicated. Excitation wave-
length
<
3
×
10
5
W
/
cm
2
at 785 nm, collection time 1 s. Abbreviations: cps, counts
per second; ν, stretching mode; ω, wagging mode; δ, bending mode; Rib, ribose; Pyr,
pyrimidine; Im, imidazol
In the following we will discuss SERS measurements of the pollen cellular
fraction in more detail.
4.3.2 SERS from Pollen Cellular Fraction
Obtaining SERS spectra from pollen and in particular from the cellular inte-
rior is of interest as it may provide higher sensitivity for detection of pollen
fragments in bioaerosols, and may also enable studies of allergologically rel-
evant pollen molecular constituents. Sengupta et al. published SERS spectra
from suspensions of cottonwood and redwood pollen as well as two types of
grass and compared them with spectra from bacteria [54, 90]. The spectra were
obtained from suspensions of pollen particles in silver colloids. As the amount
of pollen used was not quantified in these experiments, it remains unclear
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