Protection of liposomes against fusion during drying by oligosaccharides is not predicted by the ... more Protection of liposomes against fusion during drying by oligosaccharides is not predicted by the calorimetric glass transition temperatures of the dry sugars
In previous studies, it has been suggested that chilling induced activation of human platelets is... more In previous studies, it has been suggested that chilling induced activation of human platelets is related to a lipid phase transition seen in membrane lipids. Those studies showed a single, surprisingly cooperative transition in human platelets, as determined by Fourier transform infrared (FTIR) spectroscopy, findings that are confirmed here with calorimetric measurements. Such transitions have now been studied in membrane fractions obtained from the platelets and it is reported that all fractions and purified phospholipids show similar transitions. In order to obtain these data it was necessary to develop means for separating these fractions. Therefore, a novel method for isolation and separation of dense tubular system (DTS) and plasma membranes in human platelets is described here. Lipid analysis showed that phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were the dominant phospholipids in both fractions, whereas cholesterol and sphingomyelin (SM) were predominantly located in the plasma membranes. Thermotropic phase transitions in the two membrane fractions, determined by differential scanning calorimetry (DSC) and FTIR spectroscopy were found to occur at about 15 degrees C, similar to the Tm of intact human platelets. These data are discussed in relation to the role of the DTS and plasma membranes in the cold-induced activation of human platelets.
Fourier-transform infrared spectroscopy (FTIR) was used to study the hydrogen-bonding interaction... more Fourier-transform infrared spectroscopy (FTIR) was used to study the hydrogen-bonding interactions that take place in vitrified carbohydrates of different chain lengths. The band position of the OH stretching band (vOH) and the shift in band position as a function of temperature were determined from the FTIR spectra as indicators for the length and strength of intermolecular hydrogen bonds, respectively. Differential scanning calorimetry (DSC) was used to corroborate the FTIR studies and to measure the change in heat capacity (delta C(p)) that is associated with the glass transition. We found that with increasing T(g), the band position of vOH increases, the wavenumber-temperature coefficient of vOH in the glassy state, WTC(g), increases, whereas (delta C(p) decreases. The positive correlation that was found between vOH and the glass transition temperature, T(g), indicates that the length of the hydrogen bonds increases with increasing T(g). The increase in WTC(g) with increasing T(g) indicates that the average strength of hydrogen bonding decreases with increasing T(g). This implies that oligo- and polysaccharides (high T(g)) have a greater degree of freedom to rearrange hydrogen bonds during temperature changes than monosaccharides (low T(g)). Interestingly, WTC(g) and delta C(p) showed a negative linear correlation, indicating that the change in heat capacity during the glass transition is associated with the strength of the hydrogen-bonding network in the glassy state. Furthermore, we report that introduction of poly-L-lysine in glassy sugar matrices decreases the average length of hydrogen bonds, irrespective of the size of the carbohydrate. Palmitoyl-oleoyl-phosphatidylcholine (POPC) vesicles were found to only interact with small sugars and not with dextran.
The Jerusalem Symposia on Quantum Chemistry and Biochemistry, 1992
... Ann E. Oliver and David W. Deamer Dept. ... FTIR spectroscopy was used to probe the secondary... more ... Ann E. Oliver and David W. Deamer Dept. ... FTIR spectroscopy was used to probe the secondary structure of peptides by comparison of the carbonyl stretching (amide I) region (Byler and SUS!, 1986; 1988; Susi and Byler, 1983). ...
Protection of liposomes against fusion during drying by oligosaccharides is not predicted by the ... more Protection of liposomes against fusion during drying by oligosaccharides is not predicted by the calorimetric glass transition temperatures of the dry sugars
In previous studies, it has been suggested that chilling induced activation of human platelets is... more In previous studies, it has been suggested that chilling induced activation of human platelets is related to a lipid phase transition seen in membrane lipids. Those studies showed a single, surprisingly cooperative transition in human platelets, as determined by Fourier transform infrared (FTIR) spectroscopy, findings that are confirmed here with calorimetric measurements. Such transitions have now been studied in membrane fractions obtained from the platelets and it is reported that all fractions and purified phospholipids show similar transitions. In order to obtain these data it was necessary to develop means for separating these fractions. Therefore, a novel method for isolation and separation of dense tubular system (DTS) and plasma membranes in human platelets is described here. Lipid analysis showed that phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were the dominant phospholipids in both fractions, whereas cholesterol and sphingomyelin (SM) were predominantly located in the plasma membranes. Thermotropic phase transitions in the two membrane fractions, determined by differential scanning calorimetry (DSC) and FTIR spectroscopy were found to occur at about 15 degrees C, similar to the Tm of intact human platelets. These data are discussed in relation to the role of the DTS and plasma membranes in the cold-induced activation of human platelets.
Fourier-transform infrared spectroscopy (FTIR) was used to study the hydrogen-bonding interaction... more Fourier-transform infrared spectroscopy (FTIR) was used to study the hydrogen-bonding interactions that take place in vitrified carbohydrates of different chain lengths. The band position of the OH stretching band (vOH) and the shift in band position as a function of temperature were determined from the FTIR spectra as indicators for the length and strength of intermolecular hydrogen bonds, respectively. Differential scanning calorimetry (DSC) was used to corroborate the FTIR studies and to measure the change in heat capacity (delta C(p)) that is associated with the glass transition. We found that with increasing T(g), the band position of vOH increases, the wavenumber-temperature coefficient of vOH in the glassy state, WTC(g), increases, whereas (delta C(p) decreases. The positive correlation that was found between vOH and the glass transition temperature, T(g), indicates that the length of the hydrogen bonds increases with increasing T(g). The increase in WTC(g) with increasing T(g) indicates that the average strength of hydrogen bonding decreases with increasing T(g). This implies that oligo- and polysaccharides (high T(g)) have a greater degree of freedom to rearrange hydrogen bonds during temperature changes than monosaccharides (low T(g)). Interestingly, WTC(g) and delta C(p) showed a negative linear correlation, indicating that the change in heat capacity during the glass transition is associated with the strength of the hydrogen-bonding network in the glassy state. Furthermore, we report that introduction of poly-L-lysine in glassy sugar matrices decreases the average length of hydrogen bonds, irrespective of the size of the carbohydrate. Palmitoyl-oleoyl-phosphatidylcholine (POPC) vesicles were found to only interact with small sugars and not with dextran.
The Jerusalem Symposia on Quantum Chemistry and Biochemistry, 1992
... Ann E. Oliver and David W. Deamer Dept. ... FTIR spectroscopy was used to probe the secondary... more ... Ann E. Oliver and David W. Deamer Dept. ... FTIR spectroscopy was used to probe the secondary structure of peptides by comparison of the carbonyl stretching (amide I) region (Byler and SUS!, 1986; 1988; Susi and Byler, 1983). ...
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