426
K. malek et al.
there is only a low intensity ν s (Ch 2 ) band and no C = o band at 1740 cm
−1
then these
bands are associated with aliphatic functional groups of proteins. For instance, the
high-frequency region was shown as a potential marker for cytoplasmic and nuclear
changes during oocyte maturation at the germinal vesicle and metaphase II stages
[26]. In addition, the position of the symmetric stretching mode of the Ch 2 groups
can be an indicator of order and disorder of the lipid-membrane, which is strongly
dependent on the composition, hydration, content of membrane proteins and other
factors [27]. In such cases, a useful parameter can be the shift in the wavenumber of
the Ch 2 stretching vibration [26] that indicates changes in acyl chain flexibility. the
shifting towards lower frequencies can also indicate an increase in the number of
trans isomers of lipids [28] or in general a different lipid environment. the former
can be related to an increase in lipid order and chain rigidity.
Furthermore, the variability of intensities of the asymmetric Ch 2 and the ester
C = o stretches in relation to amide I/II bands is also an indicator of the overall
protein/lipid ratio. Changes of this ratio due to lipid-protein metabolism also result
in spectral changes in the region below 1500 cm
−1
. A band at 1397 cm
−1
that is
assigned to the bending mode of the side chains of amino acid residues exhibits a
higher intensity for high-content of proteins in comparison to the scissoring mode
of the Ch 2 groups observed at around 1460 cm
−1
(mostly lipids).
An analysis of the ν(C = O) absorbances can also discriminate structure and composition of mitochondrial and plasma membranes in cells [27]. the C = o stretching
mode at ca. 1740 cm
−1
is attributed to triglycerides as well as to cholesterol esters
[29], while a band at 1713 cm
−1
was proposed as evidence for the presence of free
fatty acids [16]. however, this band is usually overlapped by the amide I band. Intensity alteration of the 1470–1460 cm
−1
band suggests changes in content of estercontaining macromolecules, which can be supported by similar changes observed in
the intensity of bands at 1343 (the Ch 2 wagging mode) and 1170 cm
−1
(the Co-o-C
asymmetric stretches) originating from triglycerides and cholesterol esters, respectively. In turn, the C-o vibrations of cholesterol found in atherosclerotic aortas,
contribute to a band at 1055 cm
−1
[29]. the presence of phospholipids versus lipids
can be recognized additionally by the appearance of the phosphate group bands,
especially at ca. 1088 cm
−1
. however, this band is often superimposed by sub-bands
originating from phosphodiester groups of various biomolecules [27].
15.2.3 Carbohydrates
In general, the spectral range of 1150–1000 cm
−1
is typical for carbohydrates. A
maximum at ca. 1085 and 1050 cm
−1
with a shoulder at around 1030 cm
−1
is assigned to mono- and polysaccharides as well as proteoglycans. the presence of a
particular carbohydrate is usually linked to known information about biochemical events. Its spectral profile depends on hydration but Chiriboga and co-workers
reported that for example glycogen in the cell is in a semi-hydrated form and thus
its characteristic bands are observed at ca. 1150, 1080 and 1028 cm
−1
[30]. the
K. malek et al.
there is only a low intensity ν s (Ch 2 ) band and no C = o band at 1740 cm
−1
then these
bands are associated with aliphatic functional groups of proteins. For instance, the
high-frequency region was shown as a potential marker for cytoplasmic and nuclear
changes during oocyte maturation at the germinal vesicle and metaphase II stages
[26]. In addition, the position of the symmetric stretching mode of the Ch 2 groups
can be an indicator of order and disorder of the lipid-membrane, which is strongly
dependent on the composition, hydration, content of membrane proteins and other
factors [27]. In such cases, a useful parameter can be the shift in the wavenumber of
the Ch 2 stretching vibration [26] that indicates changes in acyl chain flexibility. the
shifting towards lower frequencies can also indicate an increase in the number of
trans isomers of lipids [28] or in general a different lipid environment. the former
can be related to an increase in lipid order and chain rigidity.
Furthermore, the variability of intensities of the asymmetric Ch 2 and the ester
C = o stretches in relation to amide I/II bands is also an indicator of the overall
protein/lipid ratio. Changes of this ratio due to lipid-protein metabolism also result
in spectral changes in the region below 1500 cm
−1
. A band at 1397 cm
−1
that is
assigned to the bending mode of the side chains of amino acid residues exhibits a
higher intensity for high-content of proteins in comparison to the scissoring mode
of the Ch 2 groups observed at around 1460 cm
−1
(mostly lipids).
An analysis of the ν(C = O) absorbances can also discriminate structure and composition of mitochondrial and plasma membranes in cells [27]. the C = o stretching
mode at ca. 1740 cm
−1
is attributed to triglycerides as well as to cholesterol esters
[29], while a band at 1713 cm
−1
was proposed as evidence for the presence of free
fatty acids [16]. however, this band is usually overlapped by the amide I band. Intensity alteration of the 1470–1460 cm
−1
band suggests changes in content of estercontaining macromolecules, which can be supported by similar changes observed in
the intensity of bands at 1343 (the Ch 2 wagging mode) and 1170 cm
−1
(the Co-o-C
asymmetric stretches) originating from triglycerides and cholesterol esters, respectively. In turn, the C-o vibrations of cholesterol found in atherosclerotic aortas,
contribute to a band at 1055 cm
−1
[29]. the presence of phospholipids versus lipids
can be recognized additionally by the appearance of the phosphate group bands,
especially at ca. 1088 cm
−1
. however, this band is often superimposed by sub-bands
originating from phosphodiester groups of various biomolecules [27].
15.2.3 Carbohydrates
In general, the spectral range of 1150–1000 cm
−1
is typical for carbohydrates. A
maximum at ca. 1085 and 1050 cm
−1
with a shoulder at around 1030 cm
−1
is assigned to mono- and polysaccharides as well as proteoglycans. the presence of a
particular carbohydrate is usually linked to known information about biochemical events. Its spectral profile depends on hydration but Chiriboga and co-workers
reported that for example glycogen in the cell is in a semi-hydrated form and thus
its characteristic bands are observed at ca. 1150, 1080 and 1028 cm
−1
[30]. the