428
K. malek et al.
Benedetti and co-workers compared FtIR spectra of dried films from calf thymus dNA and RNA from baker’s yeast [23]. they showed that the asymmetric
[ν as (Po 2
−
)] and symmetric [ν s (Po 2
−
)] stretching modes of the phosphate group are
observed at ca. 1240 and 1080 cm
−1
, respectively, in the IR spectra of both nucleic
acids. However, the ν as (Po 2
−
) mode of pure RNA was reported to be at a higher
wavenumber value than that of dNA. the appearance of the two bands in IR spectra
of cells and tissues can be also attributed to phosphorylated proteins, phospholipids,
and other phosphate-containing macromolecules, as discussed above. In turn, IR
bands at 1160, 1120, 1036, 996, and 916 cm
−1
with their bandwidth are specific for
RNA. Among them, the pronounced 1120 and 996 cm
−1
bands assigned to vibrations
of the ribose and uracyl moieties, respectively, provide unique markers to detect
RNA. Although, vibrational modes of the carbohydrate Ch 2 oh and C-o groups
also appear in this spectral region, they are less intense than nucleic acids bands
[34].Increasing concentration of RNA considerably modifies the most characteristic dNA band centred at ca. 1240 cm
−1
. As mentioned in paragraph 2.1, increasing
dNA/RNA content also alters the protein profile in the region of the amide I and II
bands. Broadening of the amide I band is greater for RNA than for dNA, and additionally shoulders at 1710 and 1705 cm
−1
are observed in IR spectra of protein-nucleic acid mixtures with a high concentration of dNA and RNA, respectively [23].
In turn, Andrus and Strickland proposed cancer grading based on increasing absorbance ratio of bands at 1121 and 1020 cm
−1
assigned to RNA and dNA vibrations, respectively [35]. A value of this index indicates clinically aggressive and
clinically indolent lymphomas and it rises with lymphoma grade showing increasing RNA content. A similar observation was found in IR spectra of cervical cancer
tissues, suggesting a higher transcription rate during carcinogenesis [36].
Another example of RNA detection in monitoring biochemical events in cells
by the use of FtIR microspectroscopy was reported by Ami and co-workers [14].
In this study, the low-frequency bands of RNA, i.e. at 994 and 914 cm
−1
, along
with a dNA band at 966 cm
−1
were identified as marker bands for an analysis of
conformational and content alternations of nucleic acids in the differentiation process of embryonic stem cells. Changes in intensity of these bands revealed a low
content of dNA and a high content of RNA at beginning of differentiation. the latter decreased between 4 and 7 days with shifting of the protein amide I band. this
was interpreted as the beginning of mRNA transcription, in which dormant mRNA
could be polyadenylated and activated to produce a new phenotype of proteins. In
turn, the appearance of dNA bands at this stage of differentiation was associated
with gene transcription, in which a dNA/RNA hybrid is formed [14].
15.2.5 Deoxyribonucleic Acid (DNA)
the main dNA vibrations appear at ~ 1225 cm
−1
and 1080 cm
−1
and are assigned
to the phosphodiester asymmetric and symmetric stretching vibrations, respectively. the position of the asymmetric phosphodiester stretching vibration in dNA is
K. malek et al.
Benedetti and co-workers compared FtIR spectra of dried films from calf thymus dNA and RNA from baker’s yeast [23]. they showed that the asymmetric
[ν as (Po 2
−
)] and symmetric [ν s (Po 2
−
)] stretching modes of the phosphate group are
observed at ca. 1240 and 1080 cm
−1
, respectively, in the IR spectra of both nucleic
acids. However, the ν as (Po 2
−
) mode of pure RNA was reported to be at a higher
wavenumber value than that of dNA. the appearance of the two bands in IR spectra
of cells and tissues can be also attributed to phosphorylated proteins, phospholipids,
and other phosphate-containing macromolecules, as discussed above. In turn, IR
bands at 1160, 1120, 1036, 996, and 916 cm
−1
with their bandwidth are specific for
RNA. Among them, the pronounced 1120 and 996 cm
−1
bands assigned to vibrations
of the ribose and uracyl moieties, respectively, provide unique markers to detect
RNA. Although, vibrational modes of the carbohydrate Ch 2 oh and C-o groups
also appear in this spectral region, they are less intense than nucleic acids bands
[34].Increasing concentration of RNA considerably modifies the most characteristic dNA band centred at ca. 1240 cm
−1
. As mentioned in paragraph 2.1, increasing
dNA/RNA content also alters the protein profile in the region of the amide I and II
bands. Broadening of the amide I band is greater for RNA than for dNA, and additionally shoulders at 1710 and 1705 cm
−1
are observed in IR spectra of protein-nucleic acid mixtures with a high concentration of dNA and RNA, respectively [23].
In turn, Andrus and Strickland proposed cancer grading based on increasing absorbance ratio of bands at 1121 and 1020 cm
−1
assigned to RNA and dNA vibrations, respectively [35]. A value of this index indicates clinically aggressive and
clinically indolent lymphomas and it rises with lymphoma grade showing increasing RNA content. A similar observation was found in IR spectra of cervical cancer
tissues, suggesting a higher transcription rate during carcinogenesis [36].
Another example of RNA detection in monitoring biochemical events in cells
by the use of FtIR microspectroscopy was reported by Ami and co-workers [14].
In this study, the low-frequency bands of RNA, i.e. at 994 and 914 cm
−1
, along
with a dNA band at 966 cm
−1
were identified as marker bands for an analysis of
conformational and content alternations of nucleic acids in the differentiation process of embryonic stem cells. Changes in intensity of these bands revealed a low
content of dNA and a high content of RNA at beginning of differentiation. the latter decreased between 4 and 7 days with shifting of the protein amide I band. this
was interpreted as the beginning of mRNA transcription, in which dormant mRNA
could be polyadenylated and activated to produce a new phenotype of proteins. In
turn, the appearance of dNA bands at this stage of differentiation was associated
with gene transcription, in which a dNA/RNA hybrid is formed [14].
15.2.5 Deoxyribonucleic Acid (DNA)
the main dNA vibrations appear at ~ 1225 cm
−1
and 1080 cm
−1
and are assigned
to the phosphodiester asymmetric and symmetric stretching vibrations, respectively. the position of the asymmetric phosphodiester stretching vibration in dNA is