228
B. Czarnik-Matusewicz and Y.M. Jung
and high (700–1,150 mPa) pressure ranges and have been independently analyzed
by 2DCoS. The obtained results show increased hydration of the α-helix conformer
(low range) and the gradual transition to α′-helix (high range). In contrast, the initial
β-sheets and random coils are first transformed to an α-helix at pressures < 400 mPa
and are next transformed to an α′-helix in the high pressure range.
more recently, Wu’s group has investigated the pressure-induced structural
changes in isolated bovine serum albumin and bovine serum albumin used as a
protecting ligand for gold nanoclusters, AuNCs@BSA. In these studies, both fluorescence and IR spectroscopy assisted by 2dCoS were involved [89]. the 2dCoS
results have supported the results that under compression, more buried α-helical
structures of BSA are lost whereas in the AuNCs@BSA, a more flexible conformational state is formed at the boundary of the gold nanoclusters.
dzwolak et al. wrote a review of the application of high pressure in studies of
protein by FtIR spectroscopy [130]. the authors have also used the 2dCoS analysis to confirm the acceleration of the kinetics of h/d-exchange with temperature
upon the heating of α-lactalbumin (α-la) from 20 °C to 42.5 °C and upon a pressure increase from 0.1 mPa to 180 mPa [48]. Comparison of the synchronous and
asynchronous maps obtained for the two accelerated systems with the maps of the
control system (the time-evolving h/d exchange) has shown that the pressure and
temperature treatments differently changed the kinetics of the h/d exchange. the
comparison has revealed that the compactness inside the different secondary structures of α-la is modified differently by the applied pressure and temperature.
8.3.6 pH
modulation of ph induces specific conformational changes that are relevant for
protein function; moreover, the response of the protein structure to ph leads to
many well-defined spectral events [131]. therefore, experiments have frequently
been conducted for samples at different ph values [54, 74, 76, 77, 81]; however,
during the perturbation period, the ph of the system was maintained at a constant
level. Processes accompanying the protonation/deprotonation of the basic and acidic side chain groups result in reorganization of the tertiary and secondary protein
packing and lead to changes in the absorbance; because of their high specificity,
these changes are especially well suited for 2dCoS analysis. using 2dCoS to phperturbed mid-IR spectra of human serum albumin (hSA), murayama et al. [55]
have tried to find answers to following questions: in which direction is the secondary structure modified? and what is the role of microenvironmental changes at the
side chain sites when hSA is transformed between two isomeric forms as the ph
decreases from ph 5.0 to 3.0? the synchronous and asynchronous spectra have
been calculated from the spectral changes and have been grouped into three ph
ranges corresponding to the N isomeric form (ph 5.0–4.4), the N–F transition (ph
4.6–3.8), and the F isomeric form (ph 3.8–3.0). Because of the powerful deconvolution ability of 2dCoS, four sub-bands were detected at 1,740, 1,715, 1,705, and
B. Czarnik-Matusewicz and Y.M. Jung
and high (700–1,150 mPa) pressure ranges and have been independently analyzed
by 2DCoS. The obtained results show increased hydration of the α-helix conformer
(low range) and the gradual transition to α′-helix (high range). In contrast, the initial
β-sheets and random coils are first transformed to an α-helix at pressures < 400 mPa
and are next transformed to an α′-helix in the high pressure range.
more recently, Wu’s group has investigated the pressure-induced structural
changes in isolated bovine serum albumin and bovine serum albumin used as a
protecting ligand for gold nanoclusters, AuNCs@BSA. In these studies, both fluorescence and IR spectroscopy assisted by 2dCoS were involved [89]. the 2dCoS
results have supported the results that under compression, more buried α-helical
structures of BSA are lost whereas in the AuNCs@BSA, a more flexible conformational state is formed at the boundary of the gold nanoclusters.
dzwolak et al. wrote a review of the application of high pressure in studies of
protein by FtIR spectroscopy [130]. the authors have also used the 2dCoS analysis to confirm the acceleration of the kinetics of h/d-exchange with temperature
upon the heating of α-lactalbumin (α-la) from 20 °C to 42.5 °C and upon a pressure increase from 0.1 mPa to 180 mPa [48]. Comparison of the synchronous and
asynchronous maps obtained for the two accelerated systems with the maps of the
control system (the time-evolving h/d exchange) has shown that the pressure and
temperature treatments differently changed the kinetics of the h/d exchange. the
comparison has revealed that the compactness inside the different secondary structures of α-la is modified differently by the applied pressure and temperature.
8.3.6 pH
modulation of ph induces specific conformational changes that are relevant for
protein function; moreover, the response of the protein structure to ph leads to
many well-defined spectral events [131]. therefore, experiments have frequently
been conducted for samples at different ph values [54, 74, 76, 77, 81]; however,
during the perturbation period, the ph of the system was maintained at a constant
level. Processes accompanying the protonation/deprotonation of the basic and acidic side chain groups result in reorganization of the tertiary and secondary protein
packing and lead to changes in the absorbance; because of their high specificity,
these changes are especially well suited for 2dCoS analysis. using 2dCoS to phperturbed mid-IR spectra of human serum albumin (hSA), murayama et al. [55]
have tried to find answers to following questions: in which direction is the secondary structure modified? and what is the role of microenvironmental changes at the
side chain sites when hSA is transformed between two isomeric forms as the ph
decreases from ph 5.0 to 3.0? the synchronous and asynchronous spectra have
been calculated from the spectral changes and have been grouped into three ph
ranges corresponding to the N isomeric form (ph 5.0–4.4), the N–F transition (ph
4.6–3.8), and the F isomeric form (ph 3.8–3.0). Because of the powerful deconvolution ability of 2dCoS, four sub-bands were detected at 1,740, 1,715, 1,705, and