Conformational disorder in unsaturated phospholipids by FTIR spectroscopy

AbstractConformational disorder in liquid alkenes and in the Lα and H∥ phases of some unsaturated phospholipids has been monitored by FTIR spectroscopy. The CH2 wagging region (1330–1390 cm−1) in saturated chains contains vibrations of particular 2- and 3-bond conformational states as follows: 1341 cm−1, end-gauche (eg); 1352 cm−1, double gauche (gg); 1368 cm−1, the sum of kink and gtg states. In unsaturated chains, this spectral region revealed an additional band at 1362 cm−1 and (occasionally) a feature near 1348 cm−1. The 1362 cm−1 band is tentatively assigned to the wagging of CH2 groups adjacent to the C C bond. Substantial populations of both gg and (kink+ gtg) states are evident in the Lα phases of unsaturated phosphatidylcholines (PC's). Unsaturated phosphatidylethanolamines (PE's) are more ordered than their PC counterparts, and possess fewer gg and eg states. Chain disorder in the H∥ phase of PE's approaches that in Lα phases of unsaturated PC's. Changes in conformer distributions during the Lα →H∥ transition in 1,2-dioleoylphosphatidylethanolamine (DOPE), 1-palmitoyl,2-oleoylphosphatidylethanolamine (POPE), 1,2-dielaidoylphosphatidylethanolamine (DEPE), and N-methyl-DOPE(N-MeDOPE) were semi-quantitatively estimated. For DOPE and DEPE, slight cooperative increases in both gg and (kink+ gtg) states occur, for POPE only the gg population increases and for N-MeDOPE only the kink+ gtg populations increase. These disorder increases are consistent with the small calorimetric Δ H for this transition. Difficulties in quantitative determination of conformational disorder in unsaturated chains are discussed

Odorant Receptors Govern the Formation of a Precise Topographic Map

AbstractOlfactory neurons expressing a given odorant receptor project with precision to 2 of the 1800 glomeruli within the olfactory bulb to create a topographic map of odor quality. We demonstrate that deletions or nonsense mutations in the P2 odorant receptor gene cause the axons of these cells to wander rather than converge on a specific glomerulus. Receptor substitution experiments that replace the P2 gene with the coding region of the P3 gene result in the projection of P3→P2 axons to a glomerulus touching the wild-type P3 glomerulus. These data, along with additional receptor substitutions, indicate that the odorant receptor plays an instructive role in the establishment of the topographic map

Applications of Fourier Transform Infrared (FT-IR) Microscopy to the Study of Mineralization in Bone and Cartilage

Knowledge of the phase, composition, and crystallite size and perfection of the mineral in normal and abnormally calcified tissues provides insight into the mechanism by which this mineral was deposited. These data also can be used to develop rational therapies for pathological conditions characterized by abnormal mineral deposition. As illustrated in this review, coupling of an optical microscope with a Fourier transform infrared (FT-IR) spectrophotometer permits the mapping at 20 μm spatial resolution of changes in mineral characteristics (content, particle size, composition) in the growth plate, in bone biopsies, in mineralizing cell culture systems, and in soft tissue calcifications. Based on the infrared properties of apatitic compounds, and comparisons with x-ray diffraction data, correlations have been established from which mineral parameters can be determined. The validity of these spectral correlations has been demonstrated by independent measurements of mineral content (ash weight), and crystal particle size (dark field electron microscopy)

Secondary structure in lung surfactant SP-B peptides: IR and CD studies of bulk and monolayer phases

AbstractPulmonary surfactant protein SP-B is known to facilitate adsorption and spreading of surfactant components across the air/water interface. This property appears essential for in vivo function in the alveolar subphase and at the air/alveolar surface. Three peptides with amino acid sequences based on SP-B containing predicted α-helical regions (SP-B1-20, SP-B9-36A, SP-B40-60A) have been synthesized to probe structure-function relationships and protein-lipid interaction in bulk phase and monolayer environments. IR and CD studies are reported along with traditional surface pressure-molecular area (π-A) isotherms and IR reflection-absorption spectroscopy (IRRAS) investigations conducted at the air/water interface. In bulk phase, helix-promoting environments (methanol and aqueous dispersions of lipid vesicles), SP-B1-20 and SP-B9-36A contained significant amounts of α-helical structure, whereas varying degrees of α-helix, random coil, and β-sheet were observed in aqueous solutions and monolayers. The most striking behavior was observed for SP-B9-36A, which displayed reversible surface pressure-induced β-sheet formation. Bulk phase lipid melting curves and monolayer experiments with peptide-lipid mixtures showed subtle differences in the degree of bulk phase interaction and substantial differences in peptide surface activity. The uniqueness of IRRAS is emphasized as the importance of evaluating secondary structure in both bulk phase and monolayer environments for lung surfactant peptide mimics is demonstrated

Frege's paradox.

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Linguistics and Philosophy.MICROFICHE COPY AVAILABLE IN ARCHIVES AND HUMANITIES.Vita.Bibliography : leaves 231-236.Ph.D

Smooth muscle cell specific deletion of the PKGIα target RGS2 induces vascular dysfunction and hypertension

International audiencen.