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Biomedical subjects

J W Kauffman

Publications and source records attributed to J W Kauffman.

At least 19 recordsLinked to original sources
PubMed1992

The effects of cholesterol oxidation products in sickle and normal red blood cell membranes.

The oxysterol content in normal and sickle red blood cell (RBC) membranes was assessed using thin-layer chromatography and capillary gas chromatography/mass spectrometry. Several more oxysterols were present in sickle RBCs compared to normal RBCs. Sickle RBC membranes had a higher concentration of 5 alpha,6 alpha-epoxycholesterol, 5 alpha-cholestane-3 beta,5,6 beta-triol, 7-ketocholesterol and 19-hydroxycholesterol than normal RBC membranes. The increased oxysterols in sickle RBC may be an effect of the increased oxidative stress which occurs in sickle RBC membranes. Physical characteristics of normal and sickle RBC membrane ghosts with and without inserted oxysterols were examined by Fourier transform infrared spectroscopy. The data are consistent with a greater sterol content in sickle cells compared to normal RBC membranes, and a possible oxysterol-cholesterol synergism.

Cholesterol↗
PubMed1991

Effect of inserted oxysterols on phospholipid packing in normal and sickle red blood cell membranes.

Fourier transform infrared (FTIR) spectroscopy was used to examine the effect of oxysterol insertion into normal and sickle RBC membranes and the total lipid extracts of the membranes. Examination of the FTIR C-H stretch and fingerprint regions reveal that the insertion of 7 alpha- and 7 beta-hydroxycholesterol has the greatest effect on the fluidity of RBC membranes and lipid extracts. The results confirm the observation that sterol molecules are oriented in the membrane so that the 7 position is located in the phospholipid head group region at the lipid/water interface. The substitution of a keto for a hydroxy group at the number seven position decreases the effect of the sterol on membrane packing.

Anemia, Sickle Cell↗
PubMed1986

The influence of ion species on phosphatidylcholine bilayer structure and packing.

The effects of various monovalent cations and anions on the bilayer packing and structure of dipalmitoylphosphatidylcholine were studied using X-ray diffraction and differential scanning calorimetry. It was observed from the X-ray diffraction studies that monovalent salts, in general, have no effect on bilayer packing. The results of DSC studies on metal chloride systems are consistent with the interpretation that cations in general and Li+ in particular bind to DPPC bilayers. The effect of potassium salts on pre- and main-transition temperatures suggest that anions, such as Acetate-, also significantly bind to DPPC head groups.

Anions↗
PubMed1986

The influence of oxygenated sterol compounds on dipalmitoylphosphatidylcholine bilayer structure and packing.

Fourier Transform Infra-red and Raman Spectroscopies indicate that 7 alpha-hydroxycholesterol and 7-ketocholesterol have a diminished capacity to condense (increase the packing order of) fluid-state dipalmitoylphosphatidylcholine (DPPC) acyl chains when compared with the effects of cholesterol and the other oxidized sterols studied. DPPC head groups were also more ordered by 7-ketocholesterol over the temperature range 10 degrees - 70 degrees C. Primary effects of these sterols appear to be associated with the hydrophillic regions of the DPPC bilayer, although packing arrangements with acyl chains are also involved. Phosphate and acyl chain ester groups were observed to possess a packing order which was invariant which indicates that these may be the target groups in the interaction with 7-ketocholesterol. A surprising observation was the synergistic amplification of the effects of 7-ketocholesterol by the presence of cholesterol in the DPPC bilayer.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1985

Oxygenated cholesterols synergistically immobilize acyl chains and enhance protein helical structure in human erythrocyte membranes.

Fourier transform infrared spectroscopy revealed that insertion of 20 alpha-hydroxycholesterol into human erythrocyte membranes (10% of total membrane sterol) immobilized the lipid acyl chains to a degree equivalent to enriching total membrane cholesterol by 50% (Rooney, M.W., Lange, Y. and Kauffman, J.W. (1984) J. Biol. Chem. 259, 8281-8285). Raman spectroscopy showed that the amount of acyl chain rotamers was not significantly altered by the presence of 20 alpha-hydroxycholesterol, indicating that acyl chain immobilization was limited to an inhibition of lateral motion. The presence of 20 alpha-hydroxycholesterol may synergistically enhance the acyl-chain-immobilizing behavior of membrane cholesterol. In addition, protein helical structure was not altered by 20 alpha-hydroxycholesterol. The insertion of 7 alpha-hydroxycholesterol into erythrocyte membranes resulted in an increase in protein helical structure which was comparable to that observed for erythrocyte membranes enriched with pure cholesterol by 50%. However, both acyl chain mobility and conformation were unchanged. These results suggest a synergistic behavior between oxysterols and cholesterol in modifying erythrocyte membrane packing.

Cholesterol↗
PubMed1984

Acyl chain organization and protein secondary structure in cholesterol-modified erythrocyte membranes.

Fourier transform infrared and Raman spectroscopies are used to study the effects of cholesterol on human erythrocyte membrane acyl chain organization (mobility and conformation) and protein secondary structure. Compared to normal red cell membranes (approximately equal to 0.8 mol of cholesterol/mol of phospholipid) (C/P), acyl chain mobility is greater for the depleted (C/P approximately equal to 0.6) and less for the enriched (C/P approximately equal to 1.2) membranes as monitored by shifts of the IR symmetric methylene C-H stretching band (2852 wave numbers, cm-1) over the temperature range 5 to 40 degrees C. There is a continuous first order trend to the IR shifts, but no evidence of a phase change for any of the three cholesterol contents. Raman scattering of C-C stretching vibrations (1065-1130 cm-1) revealed that acyl chain conformation in the three membrane preparations is in a similar state of high disorder; however, compared to depleted and control membranes, the enriched membrane acyl chains display higher order lattice packing. The alpha-helical content of membrane proteins is correlated with the relative intensity of the Raman peptide backbone C-C stretching band (940 cm-1). Spectra of cholesterol-enriched erythrocyte membranes indicate a substantial increase in protein helical structure compared to those of the cholesterol-depleted membranes.

Acylation↗
PubMed1983

Raman spectroscopic and X-ray diffraction studies of the effect of temperature and Ca2+ on phosphatidylethanolamine dispersions.

Raman spectroscopy and X-ray diffraction are used to study the effect of heat and Ca2+ on dimyristoylphosphatidylethanolamine dispersions. Unlike phosphatidylcholine dispersions, dimyristoylphosphatidylethanolamine bilayers (at pH 8) require heating above Tm in order for hydration to occur and apparently bind Ca2+ at very low levels. These results are related to models for membrane fusion.

Calcium↗
PubMed1981

Raman spectroscopy of the thermal properties of reassembled high-density lipoprotein: apolipoprotein A-I complexes of dimyristoylphosphatidylcholine.

Isolated complexes of apolipoprotein A-I (apoA-I), the major apoprotein of human plasma high-density lipoproteins, and dimyristoylphosphatidylcholine (DMPC) have been prepared and studied by differential scanning calorimetry (DSC) and Raman spectroscopy. DSC studies establish that complexes having lipid to protein ratios of 200, 100, and 50 to 1 each exhibit a broad reversible thermal transition at Tc = 27 degrees C. The enthalpy of lipid melting for each of the three complexes is about 3 kcal/mol of DMPC. Raman spectroscopy indicates that the physical state of lipid molecules in the complexes is different from that in DMPC multilamellar liposomes. Analysis of the C-H stretching region (2800-3000 cm-1) of the complexes and of the pure components in water suggests that below 24 degrees C (Tc for DMPC) there is considerably less lateral order among lipid acyl chains in the complexes than in DMPC liposomes. Above 24 degrees C, these types of interactions appear to contribute equally or slightly less to the complex structure than in pure DMPC. The temperature dependence of peaks in the C-C stretching region (1000-1180 cm-1) reveals a continuous increase in the number of lipid acyl chain C-C gauche isomers over a broad range with increasing temperature. Compared to liposomes, DMPC in the complexes has more acyl chain trans isomers at temperatures above 24 degrees C; at temperatures above ca. 30 degrees C, trans isomer content is about the same for complexes and liposomes. A large change was observed in a protein vibrational band at 1340 cm-1 for pure vs. complexed apoA-I, indicating that protein hydrocarbon side chains are immobilized by lipid binding. The Raman data indicate that the reduction in melting enthalpy for complexes DMPC (approximately 3 kcal/mol) compared to that for free DMPC (approximately 6 kcal/mol) is due to reduced van der Waals interactions in the low-temperature lipid phase.

Apolipoprotein A-I↗
PubMed1978

Raman spectroscopy of intact feline corneal collagen.

The Raman Spectrum of Collagen is presented from feline corneas which were fresh and intact, heat denatured, and incubated in 2H20. Two bands in the amide I region at approx. 1630 cm-1 and approx. 1660 cm-1 and two bands at ca. 1270 cm-1 and 1247 cm-1 in the amide III region appear in the Raman spectrum of fresh and heat denatured corneal collagen. The two amide III bands have been assigned to amide III vibrations in the polar and non-polar regions of the protein. Only one small amide I band at approx. 1650 cm-1 appears when corneas are treated with 2H2O suggesting that some portion of the Raman peaks in the amide I region for corneas in water is associated with water vibrations. Feline corneal collagen fibrils do not appear to dissociate appreciably upon heating to 70 degrees C. In fact, heated corneas appear structurally similar to corneas aged 30 h at 50 degrees C. We suggest that the swelling induced by heating and aging is predominantly caused by water being absorbed and remaining between the collagen fibrils, causing a slightly more disordered collagen matrix.

Animals↗
PubMed1977

Interactions between segmented polyurethane surfaces and the plasma protein fibrinogen.

Surfaces of a segmented polyurethane were varied by casting on poly(ethylene terephthalate) (PET) and glass substrates, and were characterized through infrared-attenuated total-reflection spectroscopy (ATR). Surfaces cast on glass substrates showed a higher content of polyether segments, whereas those cast on PET contained a higher relative concentration of aromatic segments. Adsorption, and possible conformational changes of fibrinogen, were found to be more substantial on polymer surfaces having a higher content of polyether segments. It is concluded that the relatively good blood compatibility of segmented polyurethanes is partly due to the presence of peptide-like bonds on aromatic segments.

Adsorption↗
PubMed1977

Capacitance studied of syntheric phospholipid Langmuir films.

Synthetic phosphatidylcholine Langmuir films have been incorporated into metal-insulator-metal (MIM) thin film junctions. The capacitance characteristics of these junctions have been studied as a function of temperature, the number of lipid layers in the insulating layer, and the length of the hydrocarbon chains of the lipid molecule. The thickness of the oxide layer on the base aluminum electrode has been determined to be larger than or equal to 11 A, and its effects on the capacitance characteristics have been considered in some detail. Indications of phase transitions in the temperature dependence of the capacitance imply that the basic lemellar arrangement of the lipid molecules is retained even after the samples are subjected to a dehydrating vacuum annealing process. An examination of the effects of varying the hydrocarbon chain length and salt content of the subphase during sample fabrication showed that capacitance characteristics of the MIM junction are very sensitive to small structural changes in the insulating layer.

Electric Conductivity↗
PubMed1977

The noneffect of a large linear hydrocarbon, squalene, on the phosphatidylcholine packing structure.

The interaction of squalene with liposomes and monolayers of dipalmitoyl phosphatidylcholine (DPL) has been studied by differential scanning calorimetry, Raman spectroscopy, and surface potential measurements. Mole ratios of squalene to DPL up to 9 to 1 were studied. In contrast to small, nonpolar molecules, which profoundly influence the structure of lipid bilayers as detected by changes in both their thermodynamic phase transition parameters and membrane fluidity, this large, nonpolar, linear hydrocarbon is devoid of such influences. It is clear from our data that a large nonpolar molecule such as squalene, having no polar group that might anchor it to the aqueous interface, cannot intercalate between the acyl chains either below or above the phase transition of DPL. This behavior is not compatible with models that treat the bilayer interior as a bulk hydrocarbon, and suggests that great caution should be exercised in extrapolating partition coefficients based on bulk hydrocarbon measurements to lipid bilayers.

Liposomes↗
PubMed1976

Laser Raman spectroscopy of lipid-protein systems. Differences in the effect of intrinsic and extrinsic proteins on the phosphatidylcholine Raman spectrum.

Laser Raman spectroscopy is used to examine the interactions of intrinsic and extrinsic proteins with the lipid layer structure. The interactions of cytochrome c and cytochrome c oxidase with lipids have been well established by others using a variety of techniques. Cytochrome c is thought to act as an extrinsic membrane protein while cytochrome c oxidase is thought to act as an intrinsic membrane protein. The lipid-cytochrome c and lipid cytochrome c oxidase systems are used to assist in interpreting the spectral changes due to extrinsic and intrinsic protein interactions. The two types of proteins examined produced differential changes in the lipid hydrocarbon C-H stretch Raman modes for both dimyristoyl and dipalmitoyl phosphatidylcholine. The plasma proteins albumin and fibrinogen were also found to differentially affect the lipid hydrocarbon C-H stretch Raman nodes. These proteins appear to interact with lipids in an extrinsic manner different from that of cytochrome c.

Animals↗
PubMed1976

Raman spectroscopic detection and examination of the interaction of amino acids, polypeptides and proteins with the phophatidylcholine lamellar structure.

Raman spectral peaks in the vicinity of 1100 and 2900 cm-1 for phosphatidylcholine were found to be sensitive to interactions with amino acids, polypeptides and plasma proteins. The amino acids L-luecine, L-isoleucine, L-tryptophan, L-arginine HCl, L-histidine HCl, L-threonine and L-aspartic acid decreased the dipalmitoyl phosphatidylcholine Raman intensity ratio I1064/I1089 indicating an increase in the gauche hydrocarbon chain character of the lipid. The increase in the lipid approx. 2930 cm-1 peak intensity in relation to the approx. 2850 and approx. 2890 cm-1 peaks upon the addition of the amino acids L-arginine HCl, L-histidine-HCl and L-lysine-HCl to the lipid dispersion indicates that the lipid hydrocarbon chain environment becomes more polar in their presence. The lipid-alamethecin and lipid-valinomycin interactions produced a decrease in the lipid Raman intensity ratio I1064/I1089 again indicating an increase in the gauche hydrocarbon chain character of dicyristoyl phosphatidylcholine while producing no change in this ratio for dipalmitoyl phosphatidylcholine. Human fibrinogen and bovin serum albumin were found to increase the I2890/I2850 dimyristoyl phosphatidylcholine Raman intensity ratio while decreasing the I2850/I2930 dimyristoyl phosphatidylcholine Raman intensity ratio indicating that the lipid underwent a conformational change and that the hydrocarbon chain environment was more polar in the presence of albumin or fibrinogen.

Amino Acids↗
PubMed1975

Effect of ions on phospholipid layer structure as indicated by Raman spectroscopy.

Various anions and cations are found to induce changes in the layered structure of phosphatidylcholine-water systems as indicated by Raman Spectroscopy. From the ratio of Raman intensities, I1064/I1089, it is inferred that dipositive ions decrease the proportion of gauche character in the hydrocarbon chains, with the relative influence being: Ba2+ less than Mg2+ less than Ca2+ similar to Cd2+. Unipositive ions (Li+, K+ and Na+) produce no observed changes in the Raman spectrum of the lecithin dispersion. The proportion of gauche character of the hydrocarbon chains is found to be nearly independent of the anion for: Br-, Cl-, acetate-, I-, ClO4-, CNS- and SO42-. Dispersions prepared with a solution of KI+I2 produced Raman spectra in which the 1089cm-1 peak, which is characteristic of random lipid chains, was greatly intensified, presumably because of the presence of I3- which is known to penetrate the lipid lamellae. The observed trends are discussed.

Anions↗
PubMed1975

A calorimetric and monolayer investigation of the influence of ions on the thermodynamic properties of phosphatidylcholine.

The effects of various ions and 2H2O on the thermal properties of phosphatidylcholine dispersions were studied using differential scanning calorimetry and the change in the surface potential of monolayers with temperature. The phosphatidylcholine in 2H2O dispersion exhibits a slightly higher transition temperature and lower enthalpy of melting than a phosphatidylcholine in H2O dispersion. Monovalent (H+, Na+, and Li+) and some divalent cations of chloride salts (Ba2+, Mg2+, and Sr2+) have no effect on the thermal properties of phosphatidylcholine, while halide salts of the di-positive ions Cd2+ and Ca2+ have an effect on both the enthalpy of melting and transition temperature. No effect attributable to the metal ion was observed in non-halide salts of cadmium. The chloride salt of La3+ has no effect on lipid thermal properties whereas that of Fe3+ affects the transition temperature. The enthalpy of melting of phosphatidylcholine in one molar solutions of potassium salts increases in the order: CNS minus greater than acetate greater than I minus. Such large, polarizable anions clearly interact with phosphatidylcholine and must therefore also confer a negative charge on the lipid. The potassium salt of SO4-2 minus has no effect. Possible origins of the observed trends are discussed.

Anions↗