Biomedical subjects
Publications and source records attributed to W Hübner.
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The conformation and thermodynamic stability of the four polymeric carbohydrate-specific bacterial recognition proteins K88ab, AFA-1, NFA-1, and CFA-1 and their monomeric subunits that can be obtained by variation of pH were studied by infrared spectroscopy and differential scanning microcalorimetry. For NFA-1, a pH-dependent dissociation of the polymeric form cannot be achieved due to the stronger interactions of the neighboring subunits. Generally, no alterations in secondary structure are observed between the monomeric and the polymeric proteins. All adhesins reveal a high degree of beta-sheet structure (40-55%), while the alpha-helix component is of minor importance (10-20%). The adhesins investigated in this study revealed unusually high denaturation temperatures (69-104 degrees C) and stabilizing Gibbs energies, delta G (40-125 kJ/mol), compared to common globular proteins. Statistical deconvolution of the DSC curves yields a two-state transition of K88ab, NFA-1, and the monomeric CFA-1 and the existence of intermediate states for AFA-1 and polymeric CFA-1 during the denaturation process. The irreversible denaturation of K88ab, AFA-1, and CFA-1 is explained by aggregation of the polypeptide chains forming a three-dimensional network of intermolecular beta-sheet-type structures. In contrast, denaturation of NFA-1 is completely reversible. At a physiologically relevant temperature of approximately 40 degrees C, we observe predenaturational events in the DSC curves of polymeric K88ab and NFA-1 with no concomittant changes in the secondary structure of these proteins.
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The 13C labeled lipid 1[1'-13C]DPPS-NH4+ and its metal salts were used to unambiguously assign all carbonyl vibrations in the infrared spectrum of phosphatidylserines. It is shown that the C=O stretching band at 1741 cm-1 of phosphatidylserines previously assigned to the sn-1 C = O vibration contains contributions from both the sn-1 and the sn-2 carbonyls. The C=O stretching band at frequencies between 1715 and 1730 cm-1 previously assigned to the sn-2 C=O vibration also contains contributions from both carbonyl groups. The frequency dependence observed with the ester carbonyls primarily reflects hydrogen bonding and the polarity of the immediate vicinity. Conformational changes are accounted for in terms of frequency shifts if the conformational change involves the disposition of the C=O groups and in turn the hydrogen bonding properties. The infrared spectra of phospholipids dispersed in aqueous medium in the liquid crystalline state are inconsistent with a simple phospholipid conformation, e.g., with a conformation as found in the single-crystal structure of 1,2-dimyristoyl-sn-phosphatidylcholine and 1,2-dilauroyl-rac-phosphatidylethanolamine. The spectra support the hypothesis proposed earlier (Hauser et al., Biochemistry, 1988) on the basis of existing single-crystal phospholipid structures and NMR evidence. The hypothesis states that several conformations are present in liquid crystalline phospholipid dispersions.(ABSTRACT TRUNCATED AT 250 WORDS)
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The complete thermodynamic profile for the non-intercalative binding of berenil to the alternating copolymer poly d(AT) and to the homopolymer poly (dA) x poly (dT) was investigated. Differential Scanning Calorimetry (DSC) and UV absorbance spectroscopy have been used to characterize and to compare the binding of berenil to the different synthetic polymers. Both double stranded DNA's show two types of binding; one stronger binding mode at low berenil concentrations and a weaker, in the case of poly d(AT)-berenil complexes slightly cooperative binding mode at higher drug to base pair ratios. For the interaction of berenil with poly d(AT) the thermodynamic data delta G(bind)0 = -33 kJ/mol drug, delta H(bind)0 = -29 kJ/mol of drug and delta S(bind)0 = +13 J/Kmol of drug were calculated. For the minor groove binding of berenil to poly (dA) x poly (dT) the following values were obtained: delta G(bind)0 = -34 kJ/mol of drug, delta H(bind)0 = -25 kJ/mol of drug and delta S(bind)0 = +30 J/Kmol of drug. Temperature-dependent UV absorbance spectroscopy revealed for both duplexes a biphasic "melting" behavior. However, the saturated nucleic acids (drug to base pair ratio 0.33) "melted" monophasically and with a decreased length of the cooperative unit. The obtained apparent equilibrium constants K(app) for the complexation with the discharged drug molecule showed to be a sensitive function of the ionic environment. But in contradiction to the expected release of two counterions into the solvent only a value of 1.0 was observed for the alternating copolymer poly d(AT). The complexation of berenil with poly (dA) x poly (dT) is followed by a release of 1.4 ions indicating stronger electrostatic interactions. For both polynucleotides the predicted release of two ions is not achieved. This is due to the presence of a binding mode, which involves less electrostatic interactions. From the complete data set it is proposed that the mode of binding is closely related to that found for the analogue minor groove binders DAPI and netropsin.
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Several techniques for achieving palliative ureteral occlusion in cases of underlying malignant diseases are known to exist. We performed nine ureteral occlusions on seven patients, using two different techniques (occlusion by detachable balloon and by "Harzmann Olive"). Initially, complete occlusion of all ureters was attained; in two cases a second occluding intervention had to be carried out after a period of 6 and 14 weeks. Six of seven patients enjoyed a marked improvement of their quality of life after occlusion. Complications were down to a minimum. In comparison with other techniques described in the literature, Harzmann's method seems to be the simplest, as well as the most fully developed one. It may also be recommended for patients in an advanced tumor stage.
Fourier transform infrared (FT-IR) spectroscopy was used to determine whether intramolecular hydrogen bonding between the C-OH and P-OH groups exists in beef heart cardiolipin (CL) or in hydrogenated beef heart cardiolipin (18:0-CL) as compared to the synthetic 2'-deoxy analogue of cardiolipin (16:0-dCL). Such intramolecular hydrogen bonding would provide a structural basis for proton conduction on the molecular level. In aqueous dispersions at 20 degrees C, both 18:0-CL and 16:0-dCL exist in the gel phase as bilayers with gel to liquid-crystalline transitions (Tm) at 61 and 56 degrees C, respectively, whereas the unsaturated CL exists in the non-bilayer (hexagonal II) state. Evidence for intramolecular hydrogen bonding of the C-OH group in aqueous dispersions of 18:0-CL is provided by the large increase in Tm observed on changing the aqueous medium from H2O to D2O but specific hydrogen-bonded C-OH...PO2- species cannot be identified because water molecules also compete for the PO2- binding sites. However, C-OH...PO2- hydrogen bonds can be identified in dry films of the sodium salt of 18:0-CL or in CCl4 solution. In contrast, such hydrogen bonds cannot be formed in the deoxy analogue (16:0-dCL) indicating that the central C-OH group in 18:0-CL could provide a structural basis for proton conduction, involving the phosphate groups.
In 21 male dogs a 4- to 10-cm sections of the urethra was replaced by an autologous vein graft. After an observation period of 21-380 days (mean 118), the results of radiological, endoscopic, macroscopic and histological examination were evaluated for 19 animals; 2 of the animals died perioperatively. Micturition was normal in 18 of 19 animals until they were killed. One animal died on the 30th day due to a high-grade meatal stenosis with a subsequent episode of urine retention and ascending urinary infection. Gross examination of the graft in this animal, however, revealed a good result. The local surrounding tissue was found to be ideal in 11 animals, and 5 showed satisfactory results. Three times we observed a pronounced stenosis, so that in these cases results were judged to be unsatisfactory. Postmortem examinations showed the neo-urethra to be a tube made up of connective tissue completely lined by urothelium. In our opinion the results of these animal experiments could at least be equalled in clinical application.
Oriented multilayers of 1-myristoyl-2(1-13C)-myristoyl-sn-glycero-3-phosphatidylcholine (2[1-13C]DMPC) and 1-palmitoyl-2(1-13C)-palmitoyl-sn-glycero-3-phosphatidylcholine (2[1-13C]DPPC) were investigated by use of attenuated total reflection infrared spectroscopy with polarized light. Experiments were performed with the aim to determine the orientation of the two ester groups in these phospholipids in the solid state and in the hydrated state at temperatures below and above the respective gel to liquid-crystalline phase transitions. Substitution of the naturally occurring 12C carbonyl carbon atom by 13C in the ester group of the sn-2 chain of DMPC and DPPC shifts the infrared absorption of the carbonyl double bond stretching vibration to lower frequency. This results in two well-resolved ester C=O bands which can be assigned unequivocally to the sn-1 and sn-2 chains as they are separated by more than 40 cm-1. The two ester CO-O single bond stretching vibrations of the molecular fragments-CH2CO-OC-are also affected and the corresponding infrared absorption band shifts by 20 cm-1 on 13C-labeling of the carbonyl carbon atom. From the dichroic ratios of the individual ester bands in 2(1-13C)DMPC and 2(1-13C)DPPC we were able to demonstrate that the sn-1 and sn-2 ester C=O groups are similarly oriented with respect to the bilayer plane, with an angle greater than or equal to 60 degrees relative to the bilayer normal. The two CO-O single bonds on the other hand have very different orientations. The CH2CO-OC fragment of the sn-1 chain is oriented along the direction of the all-trans methylene chain, whereas the same molecular segment of the sn-2 carbon chain is directed toward the bilayer plane. This orientation of the ester groups is retained in the liquid-crystalline phase. The tilt angle of the hydrocarbon all-trans chains, relative to the membrane normal, is 25 degrees in the solid state of DMPC and DPPC multibilayers. In the hydrated gel state this angle varies between 26 degrees and 30 degrees, depending on temperature. Neither the orientation of the phosphate group, nor that of the choline group varies significantly in the different physical states of these phospholipids.
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The barotropic behavior of aqueous dispersions of two representative omega-cyclohexyl phosphatidylcholines was investigated by pressure-tuning Fourier transform infrared spectroscopy. In the even-numbered homologue, 1,2-di-14-cyclohexyltetradecanoyl-sn-glycero-3-phosphocholine (14cyPC), the lipid molecules are orientationally disordered until the applied pressure reaches 2.1 kbar. This pressure marks the onset of correlation field splitting of the scissoring and rocking modes of the linear chain methylenes, as well as that of the cyclohexyl ring methylenes. It indicates immobilization of the entire acyl chains, whereby the zig-zag planes of the neighboring straight chain all-trans methylenes are oriented mainly perpendicular to each other. As judged from the magnitude of the correlation field splittings, the interchain interaction is weaker in 14cyPC than that in linear lipids (e.g., DMPC or DPPC). Upon an increase in pressure, up to 20 kbar, the zig-zag methylene planes in 14cyPC undergo a gradual transformation to a parallel orientation. In the odd-numbered homologue, 1,2-di-13-cyclohexyltridecanoyl-sn-glycero-3-phosphocholine (13cyPC), there is no correlation field splitting originating from the straight chain methylenes (up to 21 kbar). The linear, nonbranched segments of the omega-cyclohexyl chains in 13cyPC are closely packed with the all-trans methylene zig-zag planes oriented parallel to each other. There is, however, correlation field splitting of the ring methylenes, indicating interring interactions between the bulky cyclohexyl rings in opposing bilayer leaflets. There are major structural differences between the even- and odd-numbered homologues in the interfacial region, which remain even at high pressures. The ester carbonyl C = O stretching band in 14cyPC is a composite of two discrete bands which do not change considerably in intensity or frequency in the pressure range 2-20 kbar. In contrast, 13cyPC possesses an additional, low-frequency C = O stretching component at low pressures. As the pressure increases, the three component bands coalesce into a single C = O stretching band. Our results suggest equally oriented, fully hydrogen-bonded carbonyl groups in 13cyPC at pressures above approx. 10 kbar.
We analysed the course of 80 "stone periods" (the time that elapses between making a diagnosis and passage of a stone, operation, or an out-patient's last check-up) in 62 patients with caliceal stones prior to the development of extracorporeal shockwave lithotripsy (ESWL) and endourology. The observation time per patient averaged 7.4 years; 16% of the stones passed spontaneously and 40% were removed surgically. The infection rate was 68% and 45% of the stones increased in size during the observation period. Retrospective evaluation showed that of 32 patients who underwent surgery, only 11 procedures were performed at the appropriate time. In the remaining 21 cases the timing of surgery was judged to have been too late because of the ensuing complications. In 8 patients stone growth led to staghorn calculi, 8 had acute obstruction with incipient urosepsis, 3 had chronic urinary infection and 1 had loss of kidney function. We believe that 83% of all caliceal stones require intervention (ESWL or percutaneous nephrolithotomy) within 5 years of diagnosis. Only 11% of patients with caliceal calculi remain symptom-free after 10 years.
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