Biomedical subjects

D Naumann

Publications and source records attributed to D Naumann.

At least 37 records · Page 2Linked to original sources

PubMed1998

Evidence for a new type of outer membrane lipid in oral spirochete Treponema denticola. Functioning permeation barrier without lipopolysaccharides.

A new class of outer membrane lipid (OML) was isolated from the oral spirochete Treponema denticola strain ATCC 33521 using a phenol/chloroform/light petroleum procedure normally applied for lipopolysaccharide extraction. In addition to chemical analysis, Fourier transform infrared (FTIR) spectroscopy was applied to compare the biophysical properties of OML with lipopolysaccharides (LPS) and lipoteichoic acids (LTA). Isolated OML fractions represent 1.4% of the total dry cell weight, are about 4 kDa in size, and contain 6% amino sugars, 8% neutral sugars, 14% phosphate, 35% carbazol-positive compounds, and 11% fatty acids (containing iso- and anteiso-fatty acyl chains). Rare for outer membrane lipids, OML contains no significant amount of 3-deoxy-D-manno-octulosonic acids, heptoses, and beta-hydroxy fatty acids. The fatty acyl chain composition, being similar to that of the cytoplasmic membrane, is quite heterogeneous with anteiso-pentadecanoic acid (12%), palmitic acid (51%), and iso-palmitic acid (19%) as the predominant fatty acids present. Findings of a glycerol-hexose unit and two glycerol-hexadecanoic acid fragments indicate a glycolipid membrane anchor typically found in LTA. There was also no evidence for the presence of a sphingosine-based lipid structure. The results of FTIR measurements strongly suggest that the reconstituted lipid forms normal bilayer structures (vesicles) expressing a high membrane state of order with a distinct phase transition as typical for isolated LPS. However, in contrast to LPS, OML of T. denticola has a lower Tm near 22 degreesC and a lower cooperativity of the phase transition. The results suggest a different kind of permeation barrier that is built up by this particular OML of T. denticola, which is quite different from LPS normally essential for Gram-negative bacteria.

Cell Membrane Permeability↗

PubMed1998

The influence of poly-(L-lysine) and porin on the domain structure of mixed vesicles composed of lipopolysaccharide and phospholipid: an infrared spectroscopic study.

Fourier transform infrared (FTIR) spectroscopy has been used to study the thermotropic phase behavior of binary lipid mixtures composed of deuterated phospholipids (PLs) and lipopolysaccharides (LPSs). Furthermore, the influence of an extrinsic high-molecular, polycationic polypeptide (poly-(L-lysine), PLL(500)) and an intrinsic membrane protein (outer membrane protein F, OmpF) on these binary mixtures was investigated by FTIR spectroscopy. "Deep rough" mutant LPS (ReLPS), isolated from Salmonella minnesota R595, and perdeuterated 1,2-dimyristoylphosphatidylethanolamine (DMPEd54) were used as model lipids. Deuteration of one of the lipids permitted the detection of lipid protein interaction with each lipid component separately. For this purpose, the symmetric >CH2 and >CD2 stretching bands were utilized as specific monitors to scrutinize the state of order of the membranes. From the individual phase transition temperatures Tm and the shape of the phase transition profiles, it is established that ReLPS and DMPEd54 are molecularly immiscible. In addition to the two domains of the pure lipid components, a third, domain-like structure is detected that may coexist with these pure domains. This domain-like structure undergoes a gel to liquid-crystalline L1 (beta <--> alpha) phase transition at temperatures distinctly different from that of the respective pure lipid domains. The nature of this type of domain is discussed in terms of a "border region" model that adequately explains the experimentally observed complex phase transition profiles. It is further demonstrated that the extrinsic polycationic polypeptide PLL(500) and the intrinsic, pore-forming protein OmpF isolated from Escherichia coli interact preferentially and highly specifically with the negatively charged ReLPS. Both the synthetic polypeptide and the pore-forming protein increased the tendency of ReLPS and DMPEd54 to segregate into distinct, well-separated domains. Whereas the transition profiles of the ternary system ReLPS/DMPEd54/PLL(500) showed the features of a phase segregation phenomenon not affecting the transition temperatures of the pure lipid components, the ternary system composed of ReLPS/DMPEd54 and OmpF exhibited phase transition curves that were characterized by an unspecific (DMPEd54/OmpF) and a strong and unique (ReLPS/OmpF) type of lipid-protein interaction. Furthermore, semiquantitative estimations supported the supposition that OmpF might be able to induce bilayer asymmetry in preformed symmetrical ReLPS/DMPEd54 vesicles.

Bacterial Proteins↗

PubMed1998

FT-IR microspectroscopic imaging of human carcinoma thin sections based on pattern recognition techniques.

FT-IR microspectroscopic maps of unstained thin sections from human melanoma and colon carcinoma tissues were obtained on a conventional infrared microscope equipped with an automatic x, y stage. Mapped infrared data were analyzed by different image re-assembling techniques, namely functional group mapping ("chemical mapping") and, for the first time by cluster analysis, principal component analysis and artificial neural networks. The output values of the different classifiers were recombined with the original spatial information to construct IR-images whose color or gray tones were based on the spatial distribution of individual spectral patterns. While the functional group mapping technique could not reliably differentiate between the different tissue regions, the approach based on pattern recognition yielded images with a high contrast that confirmed standard histopathological techniques. The new technique turned out to be particularly helpful to improve discrimination between different types of tissue structures in general, and to increase image contrast between normal and cancerous regions of a given tissue sample.

Biomarkers, Tumor↗

PubMed1996

Refolding of thermally and urea-denatured ribonuclease A monitored by time-resolved FTIR spectroscopy.

We undertook a first detailed comparative analysis of the refolding kinetics of ribonuclease A (RNase A) by time-resolved Fourier transform infrared spectroscopy. The refolding process was initiated either by applying a temperature jump on the thermally denatured protein or by rapid dilution of a concentrated [13C]urea solution containing the chemically unfolded protein. The dead time of the injecting and mixing devices and the time-resolution of the spectrometer permitted us to monitor the refolding kinetics in a time range of 100 ms to minutes. The infrared amide I' band at 1631 cm-1 was used to directly probe the formation of beta-sheet structure during the refolding process. The aromatic ring stretching vibration of tyrosine at 1515 cm-1 was employed as a local monitor that detects changes in the tertiary structure along the folding pathway. The comparative analysis of the kinetics of the beta-sheet formation of chemically and thermally denatured ribonuclease A revealed similar folding rates and amplitudes when followed under identical refolding conditions. Therefore, our kinetic infrared studies provide evidence for a high structural similarity of urea-denatured and heat-denatured RNase A, corroborating the conclusions derived from the direct comparison of the infrared spectra of thermally and chemically denatured RNase A under equilibrium conditions [Fabian, H., & Mantsch, H.H. (1995) Biochemistry 34, 13651-13655]. In detail, the kinetic infrared data demonstrate that in the time window of 0.1-30 s approximately 40% of the native beta-sheet structure in RNase A is formed in the presence of 0.6 M urea at pH* 3.6, indicating that up to 60% of the beta-structure is formed out of the time window used in this study. Temperature jump experiments in the absence of chemical denaturants exhibited faster and more complex refolding kinetics. In addition, differences in the time constants of refolding derived from the amide I' band at 1631 cm-1 and from the tyrosine vibration at 1515 cm-1 were observed, indicating that the formation of secondary structure precedes the formation of stable tertiary contacts during the refolding of RNase A.

Animals↗

PubMed1996

Adenylate kinase from Sulfolobus acidocaldarius: expression in Escherichia coli and characterization by Fourier transform infrared spectroscopy.

Adenylate kinase from the extremely thermoacidophilic archaeon Sulfolobus acidocaldarius has been overexpressed in Escherichia coli. The highly purified enzyme was characterized by Fourier transform infrared spectroscopy (FTIR). Analysis of FTIR spectra and estimation of secondary structure revealed a global protein structure similar to that of other adenylate kinases. Thermal unfolding of the protein with an estimated Tm value near 90 degrees C is irreversible due to protein aggregation. The enzyme exhibits long-term stability up to 80 degrees C, which is an excellent adaptation to the physiological growth temperature of 75-80 degrees C. Half-widths of secondary-structure-sensitive bands and hydrogen-deuterium exchange experiments revealed that in comparison to adenylate kinase from porcine muscle cytosol the Sulfolobus enzyme is characterized by a significantly more compact and rigid protein core structure, which is likely to contribute specifically to the extreme thermostability of the protein.

Adenylate Kinase↗

PubMed1996

Thermally induced hydrogen exchange processes in small proteins as seen by FTIR spectroscopy.

Fourier-transform infrared (FTIR) spectroscopy has been used to study the thermally induced exchange characteristics of those backbone amide protons which persist H-D exchange at ambient conditions in ribonuclease A, in wild type ribonuclease T1 and some of its variants, and in the histone-like protein HBsu. The H-D exchange processes were induced by increasing the thermal energy of the protein solutions in two ways: (i) by linearly increasing the temperature, and (ii) by a temperature jump. To trace the H-D exchange in the proteins, various infrared absorption bands known to be sensitive to H-D exchange were used as specific monitors. Characteristic H-D exchange curves were obtained from which the endpoints (TH/D) of H-D exchange could be determined. The H-D exchange curves, the TH/D-values and the phase transition temperatures Tm were used to estimate the structural flexibility and stability of the given proteins. It is suggested that time-resolved FTIR spectroscopy can be used to determine global stability parameters of proteins.

Amides↗

PubMed1995

Temperature-jump-induced refolding of ribonuclease A: a time-resolved FTIR spectroscopic study.

FTIR difference spectroscopy has been used for the first time to investigate the kinetics of secondary structure formation during refolding. The refolding process of ribonuclease A (RNase A) as a model system was induced by applying a temperature-jump of 60 degrees. The temperature-jump was triggered by rapidly injecting a small volume of the thermally unfolded protein solution at 80 degrees C into a special cuvette system kept at 20 degrees C. The dead-time of the injection and the time resolution of the FTIR spectrometer permitted the observation of refolding processes in a time window ranging from 170 ms to several minutes. Specifically, the formation of beta-structures and the disappearance of irregular conformations could be observed in this time interval.

Animals↗

PubMed1994

Impact of point mutations on the structure and thermal stability of ribonuclease T1 in aqueous solution probed by Fourier transform infrared spectroscopy.

We undertook a detailed comparative analysis of the infrared spectra of wild-type ribonuclease T1 and three mutants: two single mutants, Tyr-45-->Trp (Y45W) and Trp-59-->Tyr (W59Y), and a double mutant, Tyr-45-->Trp/Trp-59-->Tyr (Y45W/W59Y). These mutants were selected because they are known to affect the activity of the enzyme. The structural differences were evaluated by using peptide backbone and side-chain "marker" bands as conformation-sensitive monitors. All mutations lead to a decrease of the thermal transition temperature, though the mutation Tyr-45-->Trp affects the Tm to a lesser degree than the replacement of Trp-59 by Tyr, both in the single (W59Y) and in the double (Y45W/W59Y) mutant. Small changes in the protein backbone conformation and in the microenvironment of certain amino acids, induced by the point mutations, could be detected. In particular, we found subtle differences in the hydrogen bonding pattern of the beta-strands in the mutants W59Y and Y45W/W59Y, compared to that in wild-type RNase T1 and in the mutant Y45W. Practically identical spectra in the amide I region were obtained for the double mutant Y45W/W59Y and the single mutant W59Y, demonstrating that it is the change from Trp to Tyr in position 59 (located at the interface between the alpha-helix and a beta-strand) which affects the overall protein conformation. The mutation Tyr to Trp in position 45, on the other hand, has practically no impact on the polypeptide backbone conformation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aspergillus oryzae↗

PubMed1994

The transmembrane domains of the nicotinic acetylcholine receptor contain alpha-helical and beta structures.

The transmembrane domain of the nicotinic acetylcholine receptor (nAChR) from Torpedo californica electric tissue contains both alpha-helical and beta structures. The secondary structure was investigated by Fourier transform infrared (FTIR) spectroscopy after the extramembrane moieties of the protein from the extracellular and intracellular sides of the membrane were removed by proteolysis using proteinase K. The secondary structure composition of this membrane structure was: alpha-helical 50%, beta structure and turns 40%, random 10%. The alpha-helices are shown to be oriented with respect to the membrane plane in a way allowing them to span the membrane, while no unidirectional structure for the beta structures was observed. These findings contradict previous secondary structure models based on hydropathy plots alone.

Animals↗

PubMed1994

Intracellular calcium concentrations during metabolic inhibition in the motoneuron cell line NSC-19.

Changes in the concentrations of intracellular free calcium ([Ca2+]i) and adenine nucleotides were determined in response to metabolic inhibitors in the motoneuron cell line NSC-19. The NADH dehydrogenase inhibitor amobarbital (Amytal) and the mitochondrial uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) were used to alter energy metabolism. Exposure of cells to 5 mM Amytal did not significantly change ATP concentrations but produced transient elevations of [Ca2+]i of approximately 80 nM, which were reduced by 32% when cells were studied in Ca(2+)-free solutions. CCCP (10 microM) caused a transient reduction in ATP concentration of 33%. CCCP also produced sustained elevations of [Ca2+]i of about 280 nM, which were reduced by 47% when in Ca(2+)-free solutions. In spite of the sustained elevation of [Ca2+]i induced by CCCP, NSC-19 showed no reduction in cell viability after 48 h compared with controls. Ruthenium red, a blocker of Ca2+ uptake by mitochondria, had little effect on the CCCP-induced [Ca2+]i increment. KCl or glutamate did not produce significant changes in [Ca2+]i, indicating that these cells do not possess significant numbers of voltage-dependent Ca2+ channels or excitatory amino acid receptor-gated channels. [Ca2+]i values in these cells were modified by changes in extracellular Ca2+ concentrations. In Ca(2+)-containing solutions, inhibition of Na+/Ca2+ exchange by amiloride and bepridil led to increased [Ca2+]i, as did blockade of Ca2+ ATPase by vanadate, suggesting that membrane transporters are important in Ca2+ efflux in NSC-19. The present studies indicate that exposure of NSC-19 cells to Amytal and CCCP produces Ca2+ increments by release from internal stores, as well as by transmembrane influx. These results demonstrate that small increments in [Ca2+]i can be produced by metabolic inhibitors or other compounds and that such changes are not associated with immediate cell death. Changes in [Ca2+]i could potentially result in abnormal cell function secondary to altered action of Ca(2+)-dependent enzymes.

Adenine Nucleotides↗

PubMed1993

Secondary structure and temperature-induced unfolding and refolding of ribonuclease T1 in aqueous solution. A Fourier transform infrared spectroscopic study.

The secondary structure of ribonuclease T1 (RNase T1) in aqueous solution and its temperature-induced structural changes have been investigated by Fourier-transform infrared (FT-IR) spectroscopy. 13 to 14% alpha-helix and 32 to 33% beta-sheet were estimated from the resolution-enhanced FT-IR spectra, in agreement with the crystal structure which indicates 16% alpha-helix and 35% beta-sheet. Specific IR-marker bands are assigned to the different beta-sheet structures, to the slightly bent alpha-helix, and to beta-turn and irregular conformations present in RNase T1. The temperature dependence of the infrared spectra shows that the thermal unfolding and refolding of RNase T1 is fully reversible. This permitted the detailed analysis of structural changes that occur as a function of temperature by evaluating quantitatively the various secondary structure-related amide I band components and some amino acid side-chain vibrations as specific monitors. The secondary structure of RNase T1 is essentially retained in the temperature range between 20 and 50 degrees C. Significant perturbation of protein structure is initiated between 50 and 55 degrees C within regions of beta-sheet structures while the alpha-helix remains virtually intact up to 55 degrees C suggesting a "premelting" of RNase T1. Between 55 and 60 degrees C, a highly co-operative unfolding process is indicated by the simultaneous breakdown of all secondary structure components and by distinct changes of some specific side-chain vibrations. An analysis of the amide I band contour of RNase T1 at 70 degrees C proves that the unfolded state is predominantly, but not completely, irregular or "random coil". Residual, turn-like structures persisting even in the unfolded state are suggested by minor, turn related band components in the amide I region. From IR-spectra collected along a linear temperature gradient, intensity/temperature and frequency/temperature profiles were constructed using some peptide backbone and amino acid side-chain marker bands as local, structure-sensitive monitors. From these profiles individual transition temperatures tm and transition enthalpies delta H (van't Hoff) were calculated. The tm and delta H values revealed a small but distinct hysteresis between repetitive cycles of unfolding and refolding of the protein, suggesting slow refolding kinetics of RNase T1. Furthermore, the various infrared "marker bands" indicate a slightly different response towards temperature increase/decrease for different regions of the protein. The data demonstrate that infrared spectroscopy permits both the detailed analysis of structural changes occurring in a protein as a function of temperature and the determination of thermodynamic parameters characterizing its folded/unfolded state transition.

Amides↗

PubMed1993

Secondary structure and temperature behaviour of acetylcholinesterase. Studies by Fourier-transform infrared spectroscopy.

The secondary structure of the acetylcholinesterase and its temperature behaviour have been investigated using Fourier-transform infrared (FTIR) spectroscopy. The data are compared to the structure obtained by X-ray analysis of the crystalline enzyme. The secondary structure was determined using the spectral features observed in the amide-I band (H2O buffer) and amide-I' band (D2O buffer) at 1600-1700 cm-1, taking advantage of resolution-enhancement techniques along with least-squares band-fitting procedures. The relative amounts of different secondary-structure elements, 34-36% for alpha-helices, 19-25% for beta-sheets, 15-16% for turns and 13-17% for irregular structures, were estimated. These data, obtained with the enzyme in solution, correlate well with X-ray data of the crystalline protein [Sussman, J. L., Hard, M., Frolow, F., Oefner, C., Goldman, A., Toker, L. & Silman, I. (1991) Science 253, 872-879]. These results are also in good agreement with those obtained by computing the psi and phi angles of the peptide backbone using the Kabsch and Sanders method [Kabsch, W. & Sanders, C. (1983) Biopolymers 22, 2577-2637]. In conjunction with the X-ray data, two bands in the FTIR spectra were assigned to different populations of long and short alpha-helices. Until now this phenomenon has only been described by theoretical calculations [Nevskaya, N. A. & Chirgadze, Yu. N. (1976) Biopolymers 15, 637-648]. The relationship between the thermally induced loss of enzyme activity and secondary-structure changes has also been investigated. The decrease in enzyme activity to zero at 30-40 degrees C was accompanied only by minor changes in the secondary structure. At 55-60 degrees C, denaturation of AChE occurs. In this temperature range, all bands assigned to the various secondary-structure elements abruptly disappear in a co-operative and irreversible manner, whereas the beta-aggregation bands (at 1622 cm-1 and the corresponding high-frequency band) increase in intensity at the same rate.

Acetylcholinesterase↗

PubMed1993

Secondary structure and temperature behavior of the acetylcholine receptor by Fourier transform infrared spectroscopy.

Fourier transform infrared spectroscopy (FT-IR) was used to test the secondary structure of purified acetylcholine receptor membranes from Torpedo californica. The secondary structure was estimated using the spectral features observed in the structure sensitive region of amide I and amide I' (between 1600 and 1700 cm-1), taking advantage of Fourier self-deconvolution and second-derivative techniques along with least-squares band fitting procedures. At least six different amide I' band components could be resolved in D2O and were tentatively assigned to beta-structures (1680 and 1636 cm-1), alpha-helices (1657 cm-1), aperiodic structures and/or distorted helices (1646-1648 cm-1), and turns (1690 and 1668 cm-1), respectively. The beta-band around 1637 cm-1, in particular, turned out to be complex since it reproducibly exhibited weak features near 1630 and 1627 cm-1, thereby suggesting the presence of different chain interacting beta-structures. The band near 1657 cm-1 was assigned to alpha-helices which transverse the membrane bilayers, while 1646-1648-cm-1 component was tentatively attributed to aperiodic structures and alpha-helices localized within the "globular head" of the receptor protein protruding from the membrane surface into the surrounding water. Least-squares band fitting procedures were applied in order to estimate relative amounts of secondary structures. The results suggest 36-43%, 32-33%, 14-24%, and 18-19% for beta-, alpha-helical, turn, and "rest" structures, respectively. Additionally, the temperature- and time-dependent variations of the secondary structure was tested by evaluating the changes of amide I and amide II band components of receptor membranes dispersed in H2O and D2O.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Grouping of oral streptococcal species using Fourier-transform infrared spectroscopy in comparison with classical microbiological identification.

The grouping and identification made by Fourier-transform infrared spectroscopy (FT-IR) of 40 oral streptococcal strains was compared with their known taxonomic positions. Grouping was obtained by cluster analysis on the spectral distances between the first derivative spectra of the strains. Spectra were divided into five spectral 'windows' and cluster analysis was either on either a combination of all five windows or on a selected window. The oral streptococci were divided into two main clusters, mutans streptococci and other streptococci. This division was based mainly on the spectral information contained in the window between 1300-900 cm-1, indicative of polysaccharide and phosphate-carrying compounds. In the grouping based on the entire spectrum, species clusters could be observed for Streptococcus crista, Strep. salivarius and Strep. rattus. A few strains were placed in wrong clusters because of intra-strain variance. It is concluded that the grouping of these oral streptococcal species was good and similar to the classical taxonomy and that FT-IR might develop into a new identification method for oral streptococci.

Animals↗

PubMed1992

Fourier transform infrared (FTIR) spectroscopic investigation of the nicotinic acetylcholine receptor (nAChR). Investigation of agonist binding and receptor conformational changes by flash-induced release of 'caged' carbamoylcholine.

The binding and interaction of carbamoylcholine with the nicotinic acetylcholine receptor was investigated using photolytically released carbamoylcholine ('caged' carbamoylcholine). Upon UV flash activation of this photolabile substrate analog, characteristic changes in the IR absorbance spectrum were detected. Apart from difference bands arising from the changes of molecular structure upon photolytical release, spectral features can be attributed to the agonist upon binding to the receptor as well as to conformational changes of the receptor itself. The two photo-labile agonist analogs N-[1-(2-nitrophenyl)ethyl] carbamoylcholine iodide (cage I) and N-(alpha-carboxy-2-nitrobenzyl) carbamoylcholine trifluoroacetate (cage II), with different structures for comparison of the 1680-1540 cm-1 region sensitive for protein conformation, yielded consistent results. A preliminary interpretation in terms of substrate binding and local conformational changes of the receptor upon carbamoylcholine binding is provided, in analogy to the binding of acetylcholine, activation, and subsequent deactivation taking place during signal transduction.

Animals↗

PubMed1992

Secondary structure of streptokinase in aqueous solution: a Fourier transform infrared spectroscopic study.

The secondary structure of streptokinase (Sk) in aqueous solution was quantitatively examined by using Fourier transform infrared (FT-IR) spectroscopy. Resolution enhancement techniques, including Fourier deconvolution and derivative spectroscopy, were combined with band curve-fitting procedures to quantitate the spectral information from the amide I bands. Nine component bands were found under the broad, nearly featureless amide I bands which reflect the presence of various substructures. The relative areas of these component bands indicate an amount of beta-sheet between 30 and 37% and an alpha-helix content of only 12-13% in Sk. Further conformational substructures are assigned to turns (25-26%) and to "random" structures (15-16%). Additionally, the correlation of a pronounced component band near 1640 cm-1 (10-16% fractional area) with the possible presence of 3(10)-helices is discussed.

Amides↗

PubMed1991

Small and medium-angle X-ray analysis of bacterial lipoteichoic acid phase structure.

X-ray scattering analysis was performed on various types of bacterial lipoteichoic acid in solution. The X-ray data show that all samples investigated were characterized by a similar micellar ultrastructure (hydrophilic moiety on the outside) with a fatty acid chain conformation of the disordered, alpha-type at all temperatures between 5 degrees-53 degrees C. The size distribution of Staphylococcus aureus lipoteichoic acid micelles was sufficiently homogeneous to determine their size and some related molecular parameters by detailed small-angle X-ray scattering analysis. Nearly independent of the degree of D-alanine substitution and the ionic strength of the aqueous dispersion, an average micelle contained about 150 lipoteichoic acid molecules arranged in a spherical assembly with a diameter of about 22 nm, whereby the hydrophilic region occupied an outer shell of about 8.5 nm thickness. Based on the average chain length of lipoteichoic acid, it could be estimated that each glycerophosphate residue contributed by about 0.34 nm to the thickness of the hydrophilic shell as compared to a theoretical value of approximately 0.8 nm for a fully extended chain conformation, indicating a highly coiled conformation of the hydrophilic chain. The bearing of these findings on the properties of membrane-associated and secreted lipoteichoic acids is discussed.

Bifidobacterium↗

PubMed1991

In vivo study of the state of order of the membranes of gram-negative bacteria by Fourier-transform infrared spectroscopy (FT-IR).

Temperature-induced order/disorder transition profiles were obtained from the membranes of intact Gram-negative bacterial cells by FT-IR analysis of the frequency shifts of the acyl chain methylene symmetric stretching band as a monitor. Cells grown at different temperatures yielded distinct transition profiles. At the individual growth temperatures, however, the nearly alike frequency values indicated a very similar 'state of order' of the bacterial membranes. The FT-IR data were complemented by GC analysis of whole cell fatty acid composition. The FT-IR data obtained in vivo gave direct evidence of the adaptation of the 'state of order' and 'fluidity' of bacterial membranes to varying growth temperatures.

Cell Membrane↗