459
15 FtIR Imaging of tissues: techniques and methods of Analysis
respectively. this may indicate that a process of protein conformational change is
concomitant with demyelination following Nogo-A vaccination [140].
the family of transmissible spongiform encephalopathies (tSE), called prion
diseases, is a class of neurodegenerative diseases also associated with the presence
of misfolded protein—prion protein PrP
Sc
[141]. this belongs to the family of glycoproteins and appears in infected neurons, however deposits of PrP
Sc
are not uniformly distributed throughout neurons, even in the terminated state of the disease.
FtIR microspectroscopy studies have been focused on scrapie-infected hamsters
only and they have evidenced protein changes in neurons by the observation of an
IR band in the region of β-sheet conformation [142–144]. Worth mentioning is the
fact that no relevant spectral differences in the amide I position were found in IR
spectra recorded with the use of a globar source and single element detectors, but
only utilizing synchrotron IR radiation revealed changes in protein conformation
[144]. this was explained by the higher spatial resolution of synchrotron-based
measurements that enabled detection of small-size PrP
Sc
deposits. the synchrotronbased IR spectra show that the α-helical amide I band at 1657 cm
−1
decreases in the
infected hamsters along with a band appearing at 1637 cm
−1
. An additional peak
at 1631 cm
−1
was also observed in some neurons. the examination of over 10,000
IR spectra of control and diseased neuronal cells indicated that the majority of the
investigated cells show α-helical conformation with only a minority exhibiting a
high content of β-sheet structure in the control group in contrast to the scrapie-infected animals. Since immunostaining with the PrP specific antibody 3F4 excludes
the presence of misfolded proteins in the healthy tissues, the high concentration of
β-sheet proteins found in the infected brain tissues is proposed as an indicatior of
PrP
Sc
deposition [144].
15.5.3 Cardiac Tissue
Infrared microspectroscopic imaging has been applied to examine the extracellular
matrix of the myocardium in cardiomyopathy (CmP). Since diffuse and focal fibrosis is believed to accompany congestive heart failure, these studies have focused on
searching for the most abundant collagen type I and III deposits in the ventricular
tissue. Preliminary studies on spectral features of this tissue have demonstrated an
elevated content in collagen [145, 146]. Characteristic IR maxima of the healthy
rat heart tissue were observed in the region of carbohydrate residues attached to
collagen (1031 and 1082 cm
−1
), amide III bands of collagen (1204, 1240, and
1283 cm
−1
), and the Ch 2 wagging vibrations (1315 and 1338 cm
−1
). In addition, the
3 1 helical structure of collagen of type I gives amide I bands at 1670 and 1635 cm
−1
,
that are assigned to weakly hydrogen-bonded proline and hydroxyproline residues
and strongly hydrogen-bonded glycine carbonyls, respectively [145]. thus, the normal extracellular matrix of the myocardium can be discriminated from the diseased
tissue by spectral variations of the collagen spectral features. the first findings
from FtIR mapping of the ventricles of control and cardiomyopathis hamsters have
15 FtIR Imaging of tissues: techniques and methods of Analysis
respectively. this may indicate that a process of protein conformational change is
concomitant with demyelination following Nogo-A vaccination [140].
the family of transmissible spongiform encephalopathies (tSE), called prion
diseases, is a class of neurodegenerative diseases also associated with the presence
of misfolded protein—prion protein PrP
Sc
[141]. this belongs to the family of glycoproteins and appears in infected neurons, however deposits of PrP
Sc
are not uniformly distributed throughout neurons, even in the terminated state of the disease.
FtIR microspectroscopy studies have been focused on scrapie-infected hamsters
only and they have evidenced protein changes in neurons by the observation of an
IR band in the region of β-sheet conformation [142–144]. Worth mentioning is the
fact that no relevant spectral differences in the amide I position were found in IR
spectra recorded with the use of a globar source and single element detectors, but
only utilizing synchrotron IR radiation revealed changes in protein conformation
[144]. this was explained by the higher spatial resolution of synchrotron-based
measurements that enabled detection of small-size PrP
Sc
deposits. the synchrotronbased IR spectra show that the α-helical amide I band at 1657 cm
−1
decreases in the
infected hamsters along with a band appearing at 1637 cm
−1
. An additional peak
at 1631 cm
−1
was also observed in some neurons. the examination of over 10,000
IR spectra of control and diseased neuronal cells indicated that the majority of the
investigated cells show α-helical conformation with only a minority exhibiting a
high content of β-sheet structure in the control group in contrast to the scrapie-infected animals. Since immunostaining with the PrP specific antibody 3F4 excludes
the presence of misfolded proteins in the healthy tissues, the high concentration of
β-sheet proteins found in the infected brain tissues is proposed as an indicatior of
PrP
Sc
deposition [144].
15.5.3 Cardiac Tissue
Infrared microspectroscopic imaging has been applied to examine the extracellular
matrix of the myocardium in cardiomyopathy (CmP). Since diffuse and focal fibrosis is believed to accompany congestive heart failure, these studies have focused on
searching for the most abundant collagen type I and III deposits in the ventricular
tissue. Preliminary studies on spectral features of this tissue have demonstrated an
elevated content in collagen [145, 146]. Characteristic IR maxima of the healthy
rat heart tissue were observed in the region of carbohydrate residues attached to
collagen (1031 and 1082 cm
−1
), amide III bands of collagen (1204, 1240, and
1283 cm
−1
), and the Ch 2 wagging vibrations (1315 and 1338 cm
−1
). In addition, the
3 1 helical structure of collagen of type I gives amide I bands at 1670 and 1635 cm
−1
,
that are assigned to weakly hydrogen-bonded proline and hydroxyproline residues
and strongly hydrogen-bonded glycine carbonyls, respectively [145]. thus, the normal extracellular matrix of the myocardium can be discriminated from the diseased
tissue by spectral variations of the collagen spectral features. the first findings
from FtIR mapping of the ventricles of control and cardiomyopathis hamsters have