Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “phasing”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed2000

[Studies on retention behaviour of biopolymers on silica-based binding stationary phase in the mobile phase of acetic acid-water].

The reversed-phase chromatographic method consisting of acetic acid-water as a new mobile phase for separating biopolymers on ODS column is presented. The new mobile phase may overcome the weak points of irreversible adsorption in chromatographic separation to some degree and difficulty in concentrating proteins with lyophylization and reduce the three-component (organic solvent, ion-pairing agent and water) of typical mobile phase to two component system. Based on the retention and Z (the number of solvent molecules involving in the displacement from stationary-phase surface), log I (a constant relating to the affinity of 1 mol of solute to the bonded stationary phase), and j (a constant relating to the affinity of 1 mol of solvent to the bonded stationary phase), the elution strength of acetic acid-water mobile phase was found to be stronger than that of methanol-water-TFA. From a good linear relationship between log I and Z, it can be concluded that the interaction force between proteins and RPLC stationary phase with acetic acid-water as mobile phase is non-selective hydrophobic interaction forces. In addition, the molecular conformations of protein in acetic acid-water and methanol-trifluoroacetic acid-water were found to be different.

Acetates↗
PubMed1990

[Phase 3 and phase 4 block in the accessory pathway].

Pacemaker activity at a site proximal to the area of a conduction disturbance has been postulated as depressing conduction in late diastole (phase 4 block). To elucidate the correlation between the site of phase 4 depolarization and that of a conduction disturbance, we examined seven patients with intermittent Wolff-Parkinson-White syndrome who had tachycardia (phase 3) and bradycardia (phase 4) dependent on block in the accessory pathway. In each patient, antegrade conduction over the accessory pathway was absent at the sinus rate. During premature atrial stimulation a "window" of accessory pathway conduction was identified in each patient. The outer limit of the window ranged from 420 to 670 ms; the inner limit, from 330 to 620 ms. The duration of the window ranged from 20 to 160 ms. Four patients with orthodromic atrioventricular reentrant tachycardia exhibited preserved retrograde accessory pathway conduction. In one patient with unsustained orthodromic atrioventricular reentrant tachycardia, retrograde accessory pathway conduction also exhibited phase 3 and phase 4 blocks. The remaining two patients had no retrograde accessory pathway conduction. In two patients, retrograde concealed conduction in the accessory pathway induced by ventricular stimulation eliminated a phase 4 block in antegrade accessory pathway conduction. These results suggest that 1) an antegrade phase 4 block may have phase 4 depolarization in the accessory pathway and block at the ventricular insertion of the accessory pathway; 2) a retrograde phase 4 block may have a conduction disturbance at the atrial insertion of the accessory pathway; and 3) a complete retrograde block may occur at the atrial insertion of the accessory pathway.

Adolescent↗
PubMed1981

Yeast L double-stranded ribonucleic acid is synthesized during the G1 phase but not the S phase of the cell cycle.

The cytoplasm of Saccharomyces cerevisiae contains two major classes of protein-encapsulated double-stranded ribonucleic acids (dsRNA's), L and M. Replication of L and M dsRNA's was examined in cells arrested in the G1 phase by either alpha-factor, a yeast mating pheromone, or the restrictive temperature for a cell cycle mutant (cdc7). [3H]uracil was added during the arrest periods to cells prelabeled with [14C]uracil, and replication was monitored by determining the ratio of 3H/14C for purified dsRNA's. Like mitochondrial deoxyribonucleic acid, both L and M dsRNA's were synthesized in the G1 arrested cells. The replication of L dsRNA was also examined during the S phase, using cells synchronized in two different ways. Cells containing the cdc7 mutation, treated sequentially with alpha-factor and then the restrictive temperature, enter a synchronous S phase when transferred to permissive temperature. When cells entered the S phase, synthesis of L dsRNA ceased, and little or no synthesis was detected throughout the S phase. Synthesis of L dsRNA was also observed in G1 phase cells isolated from asynchronous cultures by velocity centrifugation. Again, synthesis ceased when cells entered the S phase. These results indicate that L dsRNA replication is under cell cycle control. The control differs from that of mitochondrial deoxyribonucleic acid, which replicates in all phases of the cell cycle, and from that of 2-micron DNA, a multiple-copy plasmid whose replication is confined to the S phase.

G1 Phase↗
PubMed2004

Aqueous phase behavior of a 1-O-phytanyl-beta-D-xyloside/water system. Glycolipid-based bicontinuous cubic phases of crystallographic space groups Pn3m and Ia3d.

Temperature- and concentration-dependent aqueous phase diagram of a novel alkylglycoside, 1-O-phytanyl-beta-D-xyloside (beta-Xyl(Phyt)), was studied using small-angle X-ray scattering, polarizing optical microscopy, and differential scanning calorimetry. The phases found in this system include an Lc phase, an Lalpha phase, an HII phase, two inverted cubic phases of crystallographic space groups Pn3m and Ia3d, and a fluid isotropic phase, FI. The phase diagram of the beta-Xyl(Phyt)/water system is similar to that for the 1-monooleylglycerol (MO)/water system, suggesting that the phase behavior is largely determined by the overall molecular shape rather than the details of surfactant molecular structure. Moreover, the structural parameters of the beta-Xyl(Phyt) liquid crystals are also similar to those of the MO/water, due primarily to the similar molecular dimensions of two molecules. As compared to the MO/water system, however, the beta-Xyl(Phyt)/water system displays a lower value of TK ( approximately 8.(5) degrees C) and a wider temperature window for the mesophases (8.(5)-120 degrees C). Moreover, beta-Xyl(Phyt) is chemically more robust than MO, as the ether linkage is more stable against hydrolysis than the ester linkage and the phytanyl chain is fully saturated.

Alkanes↗
PubMed2005

Design issues of randomized phase II trials and a proposal for phase II screening trials.

Future progress in improving cancer therapy can be expedited by better prioritization of new treatments for phase III evaluation. Historically, phase II trials have been key components in the prioritization process. There has been a long-standing interest in using phase II trials with randomization against a standard-treatment control arm or an additional experimental arm to provide greater assurance than afforded by comparison to historic controls that the new agent or regimen is promising and warrants further evaluation. Relevant trial designs that have been developed and utilized include phase II selection designs, randomized phase II designs that include a reference standard-treatment control arm, and phase II/III designs. We present our own explorations into the possibilities of developing "phase II screening trials," in which preliminary and nondefinitive randomized comparisons of experimental regimens to standard treatments are made (preferably using an intermediate end point) by carefully adjusting the false-positive error rates (alpha or type I error) and false-negative error rates (beta or type II error), so that the targeted treatment benefit may be appropriate while the sample size remains restricted. If the ability to conduct a definitive phase III trial can be protected, and if investigators feel that by judicious choice of false-positive probability and false-negative probability and magnitude of targeted treatment effect they can appropriately balance the conflicting demands of screening out useless regimens versus reliably detecting useful ones, the phase II screening trial design may be appropriate to apply.

Clinical Trials, Phase II as Topic↗
PubMed2001

Gadolinium-enhanced, vessel-tracking, two-dimensional coronary MR angiography: single-dose arterial-phase vs. delayed-phase imaging.

The purposes of our study were to investigate the benefits of using a single dose of an extracellular contrast agent for coronary magnetic resonance angiography (CMRA) and to determine the relative benefits of arterial-phase vs. delayed-phase image acquisition. The right coronary artery was imaged in 10 healthy adults using a breath-hold, two-dimensional fast gradient echo pulse sequence designed for vessel tracking (multiphase, multislice image acquisition). Pre- and postcontrast CMRA was performed. Postcontrast imaging consisted of arterial- and delayed-phase CMRA following a 15 mL bolus (single dose) of contrast media and of delayed-phase imaging following a cumulative 45 mL contrast dose (triple dose). Contrast-enhanced CMRA provided a significantly higher (P < 0.001) signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) than noncontrast CMRA. CNR was highest for single-dose arterial-phase CMRA (13.1 +/- 4.5) and triple-dose delayed-phase CMRA (13.0 +/- 4.8), followed by single-dose delayed-phase CMRA (8.4 +/- 3.5) and noncontrast CMRA (4.2 +/- 1.8). Single-dose arterial-phase CMRA provided the best visualization of the distal right coronary artery and was preferred for blinded physician assessments. We concluded that utilization of a single dose of extracellular contrast media improves CMRA, especially if timed for arterial-phase imaging. J. Magn. Reson. Imaging 2001;13:682-689.

Adult↗
PubMed1981

Analysis of the hexagonal II phase and its relations to lipidic particles and the lamellar phase. A freeze-fracture study.

Model systems of phosphatidylethanolamine (PE) and cardiolipin (DPG), as pure components and in binary mixtures with phosphatidylcholine (PC) have been morphologically analysed. The relation between the hexagonalII (HII) phase and lipidic particles as well as between the HII phase and the lamellar phase has been studied. Moreover, the periodicity of the various HII tubes was determined. (1) The periodicity of the HII phase of cardiolipin is dependent on the cation involved. DPG-Ca exhibits the smallest tube to tube distance when compared to Mg2+ and Mn2+. Moreover, the DPG-Ca tubes are quite straight, in contrast to the Mg2+ and Mn2+ tubes, which appear to be frequently curved. (2) HII tubes with two distinct diameters have been observed in HII phase containing lipid mixtures. The thickness of the HII tube is related to the composition of the tube. In the cardiolipin-lecithin system, structural separation of the pure cardiolipin HII phase has been suggested with Mg2+ and Mn2+, but not with Ca2+. (3) Models for the HII to lamellar phase transition and for the HII phase to the lipidic particles are presented. (4) Lipidic particles are exclusively found in lipid model systems, which contain HII phase favouring lipids. Morphological evidence is presented which suggests these lipidic particles represent inverted micells. These observations include: (i) there is a strong topological and quantitative relation between HII tubes and lipidic particles, (ii) lipidic particles occur densely packed in conglomerates without the presence of a smooth layer.

Animals↗
PubMed1993

Phase behavior and arrangement of molecular species in mixtures of a mixed chain and a symmetric phosphatidylethanolamine in the gel and fluid phases.

1-Octadecanoyl, 2-decanoylphosphatidylethanolamine (C(18:0)C(10:0)PE) has been reported to exhibit mixed interdigitated gel-phase packing of the phospholipid acyl chains (Mason, J.T. and Stephenson, F.A. (1990) Biochemistry 29, 590-598). In contrast, ditetradecanoylphosphatidylethanolamine (C(14:0)C(14:0)PE) packs without significant interdigitation of the phospholipid acyl chains across the bilayer center. In this report, the gel-fluid transition temperatures of C(18:0)C(10:0)PE and C(14:0)C(14:0)PE in multilamellar dispersions were determined by fluorescence anisotropy of cis-parinaric acid and trans-parinaric acid with a descending temperature scan rate of 0.67 degrees C/min. The transition mid-points detected for C(18:0)C(10:0)PE with cis-parinaric acid were 19 degrees C in water, 18 degrees C at pH 8.1, and 14 degrees C at pH 10. The phase diagram for C(14:0)C(14:0)PE and C(18:0)C(10:0)PE at pH 10 suggests complete mixing in the fluid phase and considerable immiscibility in the gel phase. Cross-linking of equimolar mixtures of C(14:0)C(14:0)PE and C(18:0)C(10:0)PE with dimethylsuberimidate at pH 10 revealed a random arrangement of the two species in the fluid phase, confirming the notion that C(18:0)C(10:0)PE and C(14:0)C(14:0)PE are miscible in the fluid phase, as determined from the phase diagram. In contrast, cross-linking of the equimolar mixture of C(18:0)C(10:0)PE and C(14:0)C(14:0)PE in the gel phase at 0 degrees C revealed a non-random arrangement, demonstrating and confirming immiscibility in the gel phase.

Chemical Phenomena↗
PubMed1983

Macrophage-mediated cytostatic activity blocks lymphoblast cell cycle progression independently in both G1 phase and S phase.

Recent work has shown that macrophage-mediated cytostatic activity inhibits cell cycle traverse in G1 and/or S phase of the cell cycle without affecting late S, G2, or M phases. The present report is directed at distinguishing between such cytostatic effects on G1 phase or S phase using the accumulation of DNA polymerase alpha as a marker of G1 to S phase transition. Quiescent lymphocytes stimulated with concanavalin A undergo a semisynchronous progression from G0 to G1 to S phase with a dramatic increase in DNA polymerase alpha activity between 20 and 30 hr after stimulation. This increase in enzyme activity was inhibited, as was the accumulation of DNA, when such cells were cocultured with activated murine peritoneal macrophages during this time interval. However, if mitogen-stimulated lymphocytes were enriched for S-phase cells by centrifugal elutriation and cocultured with activated macrophages for 4-6 hr, DNA synthesis was inhibited but the already elevated DNA-polymerase activity was unaffected. Similar results were obtained when a virally transformed lymphoma cell line was substituted as the target cell in this assay. These results show that both G1 and S phase of the cycle are inhibited and suggest that inhibition of progression through the different phases may be accomplished by at least two distinct mechanisms.

Animals↗
PubMed1992

The inverted hexagonal phase is more sensitive to hydroperoxidation than the multilamellar phase in phosphatidylcholine and phosphatidylethanolamine aqueous dispersions.

The effect of phase behaviour (hexagonal II phase and lamellar phase) on the peroxidation of membrane phospholipids has been investigated in dilinoleoyl phosphatidylcholine (DLPC)/dilinoleoyl phosphatidylethanolamine (DLPE) aqueous dispersions. Peroxidation was initiated with a water-soluble radical inducer 2,2'-azobis (2-amidino-propane) dihydrochloride (AAPN). The phospholipid morphology was monitored by 31P-nuclear magnetic resonance (NMR). Phospholipid hydroperoxides (PCOOH and PEOOH) were determined by chemiluminescence high-performance liquid chromatography (CL-HPLC). In pH-induced phase transition systems, DLPE in the bilayer state was much less oxidized than in the hexagonal II state. In composition-induced phase transition systems, the formation of total hydroperoxides and the consumption of alpha-tocopherol in the hexagonal II phase were greater than in the bilayer phase. These data suggest that the hexagonal II phase is more sensitive to hydroperoxidation than the bilayer phase in phospholipid aqueous dispersions.

Chromatography, High Pressure Liquid↗
PubMed1993

Reversed-phase liquid chromatography with microspherical octadecyl-zirconia bonded stationary phases.

Microspherical zirconia particles were synthesized and surface modified with octadecylsilane compounds for reversed-phase high-performance liquid chromatography. Monomeric and "polymeric" octadecyl-zirconia bonded stationary phases were obtained by reacting the support with octadecyldimethylchlorosilane or octadecyltrichlorosilane, respectively. The surface coverage of the zirconia-based stationary phases with octadecyl functions was approximately the same as that of octadecyl-silica sorbents. These phases were evaluated in terms of reversed-phase chromatographic properties with non-polar, slightly polar and ionic species over a wide range of mobile phase composition and pH. Monomeric octadecyl-zirconia with end-capping exhibited some metallic interactions with both basic and acidic solutes, but these interactions were greatly reduced in the presence of competing agents (e.g., tartrate ions) in the mobile phase. The "polymeric" octadecyl-zirconia sorbents exhibited higher retention than the monomeric ones with the various solutes investigated, and their residual absorptivities toward acidic solutes were much lower. The retention of non-polar and slightly polar aromatic compounds was quasi-homoenergetic on both types of octadecyl-zirconia stationary phases. Stability studies conducted at extreme pH conditions (pH 2.0 and pH 12.0), have shown that "polymeric" octadecyl-zirconia sorbents are more stable than their monomeric counterparts. These stationary phases were quite useful in the separation of polycyclic aromatic hydrocarbons, alkylbenzene and phenyl alkylalcohol homologous series, oligosaccharides, dansyl-amino acids, peptides and proteins.

Amino Acid Sequence↗
PubMed1992

Interneuronal interaction between members of quadrature phase and anti-phase pairs in the cat's visual cortex.

Interactions between adjacent simple cells recorded simultaneously from the same microelectrode placement were studied by correlational analysis. The receptive fields of pairs of such cells exhibit either 90 degrees (quadrature phase) or 180 degrees (anti-phase) phase relationships. We now show that the majority of quadrature phase pair members do not receive common input from the immediately precedent stage along the visual pathway, nor do these cells interact with each other. The anti-phase pairs show relatively strong mutual inhibition. These results suggest that each of the physically adjacent phase-related simple cells receives excitatory input from a distinct group of pre-cortical cells, and that mutual inhibitions between members of anti-phase pairs are used to construct the inhibitory subzones of these cells. We propose a model which incorporates these new results and provides a parsimonious explanation for the construction of both quadrature phase and anti-phase pairs.

Animals↗
PubMed1988

Effect of rapidity of phase separation on the efficiency of cell fractionation by partitioning in aqueous two-phase systems.

Partitioning in two-polymer aqueous phase systems is an established method for the separation, purification and characterization of biomaterials. Because of the relatively slow settling rates of these phases, a consequence of the slight difference in density between them, effort has been directed to speeding up phase separation by various means (e.g., the development of a thin-layer countercurrent distribution apparatus). This has resulted in the more rapid processing of materials. Unlike soluble materials, biological particulates (e.g., cells) generally partition between one of the bulk phases and the interface. The mechanism of cell partitioning involves cell-specific adsorption to droplets of one phase suspended in the other, subsequent to phase mixing, and the delivery of adsorbed cells to the bulk interface as the droplets settle. In this communication we show, using erythrocytes as a model, that speeding up phase separation is counterproductive when partitioning cells and results in reduced efficiency of their separation or subfractionation. The most likely reason for this result is that increasing the speed of phase settling removes the droplets of one phase suspended in the other more rapidly than cells can attach to them, thereby interfering with the mechanism whereby cells partition.

Animals↗
PubMed1995

Ab initio phase determination and phase extension using non-crystallographic symmetry.

Non-crystallographic symmetry (NCS) can be used to improve, extend or find ab initio phases to be associated with a set of observed structure amplitudes, resulting in an interpretable electron-density map. The simplest application is merely to improve the accuracy of the phases by cyclically averaging the electron density, Fourier back-transformation of the modified map, and recomputing a new map with the newly found phases. The first sophistication of this procedure is to phase extend, in successive small steps, the currently available phase information to higher resolution, where only observed amplitudes were previously available. A further sophistication is to initiate the phase extension from very low resolution where a simple geometric model, or an electron microscope image, would be consistent with the chosen resolution. A number of recent examples of virus structure determination exist where such ab initio phasing was successful. The ultimate ab initio phase determination would be to extend phases given only an estimate of the F(000) term.

Crystallography, X-Ray↗
PubMed2005

Enantiomer separation by reversed-phase liquid chromatography with novel hydrophobic phases composed of chiral cationic surfactants.

This paper describes enantiomer separation using four kinds of chiral stationary phases (CSPs) where quaternary ammonium surfactants containing L-valine diamide moieties into long alkyl chains were bound to silicagel supports by reversed phase liquid chromatography. Our aim was to examine hydrogen bonding association of the chiral moiety in hydrophobic phase brought about by aggregation of the micelle-forming surfactants on the surface. The following CSPs were thus derived from the vinyl-terminated chiral surfactants via hydrosilylation: CSP 1 from N-[3-(10-undecenoyl-L-valylamino)propyl]-N,N,N-trimethylammonium bromide, CSP 2 from N-[6-(10-undecenoyl-L-valylamino)hexyl]-N,N,N-trimethyl-ammonium bromide, CSP 3 from N-[3-(10-undecenoyl-L-valylamino)propyl]-N-octadecanyl-N,N-dimethyl-ammonium bromide and CSP 4 from N-[6-(10-undecenoyl-L-valylamino)hexyl]-N-octadecanyl-N,N-dimethylammonium bromide. The degree of hydrophobicity in the interfacial phase was observed by measuring pyrene fluorescence in aqueous media including an organic modifier. Retention of racemic N-acylleucine isopropyl esters was highest in CSP 4, followed by 3, 2, and 1. Largest alpha values toward enantiomer separation were observed for CSP 4 where the chiral moieties were kept through a hexamethylene unit apart from the polar head groups and to which another long alkyl chain was attached, as compared with those for CSP 4. In CSP 4, the chiral moiety to interact with enantiomeric solutes should be buried into the interfacial phase deeply in more extent than CSP 3. In a similar manner, CSP 2 has more effective for enantiomer separation than CSP 1. The interfacial phase of these CSPs was easily exposed to the bulk phase because of the affinity between the bulk phase and the polar head groups as well as their electrostatic repulsion. However, degree of the enantiomer separation can be controlled by the depth of the chiral moiety in the hydrophobic interfacial phase.

Chromatography, Liquid↗
PubMed2006

Bilateral phase entrainment by movement-elicited afference contributes equally to the stability of in-phase and antiphase coordination.

This study examined if and how phase entrainment by movement-related afference-- induced by passive movements of the contralateral hand-- contributes to the coordinative stability of rhythmic bimanual movements. The results revealed that phase-shifted passive movements of the dominant or the nondominant hand induced similar entrainment effects on the active movements of the contralateral hand. In terms of the phase relations between the hands only two attractors of equal strength were present, corresponding to relative phase shifts of 0 degrees and 180 degrees , respectively, i.e., to in-phase and antiphase coordination. The attractors were separated by two repellors located at relative phase shifts of +90 degrees and -90 degrees . EMG analysis indicated that the entrainment effects indeed resulted from contralateral afference, because no related changes in muscle activation were observed in the passively moved hand. It was concluded that phase entrainment by contralateral afference contributed equally to the stable performance of the bimanual in-phase and antiphase patterns, thereby enhancing the stability of these patterns relative to other phase relations between the limbs.

Adolescent↗
PubMed1995

Phase diagram of soybean phosphatidylcholine-diacylglycerol-water studied by x-ray diffraction and 31P- and pulsed field gradient 1H-NMR: evidence for reversed micelles in the cubic phase.

The phase equilibria of the system soybean phosphatidylcholine, diacylglycerol, and water has been determined using a combination of classical methods together with x-ray diffraction and NMR techniques. In particular, the extent of the phase regions of the lamellar, the reversed hexagonal, and the cubic phases have been determined. By pulsed field gradient 1H-NMR, the diffusion coefficients of all three components in a cubic phase composed of soybean phosphatidylcholine, diacylglycerol, and heavy water have been determined at 25 and 59 degrees C and also for the corresponding cubic phase composed of the chemically more well defined synthetic components 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dioleoylglycerol (DOG), and heavy water. The extension of the phase region of the cubic phase did not seem to change appreciably for the two ternary systems studied. The translational diffusion coefficient of DOPC in this cubic phase is more than an order of magnitude smaller (3 x 10(-13) m2 s-1, 59 degrees C) than the lateral diffusion coefficient of DOPC in an oriented lipid bilayer (5 x 10(-12) m2 s-1, 35 degrees C), whereas the diffusion coefficients of water and DOG were found to be about two orders of magnitude larger than DOPC at 59 degrees C. It is concluded that the cubic phase is built built up of closed reversed micelles in accordance with the suggestion from previous x-ray diffraction studies.

Diglycerides↗
PubMed1997

Influence of the intrinsic membrane protein bacteriorhodopsin on gel-phase domain topology in two-component phase-separated bilayers.

We have investigated the effect of the intrinsic membrane protein bacteriorhodopsin of Halobacterium halobium on the lateral organization of the lipid phase structure in the coexistence region of an equimolar mixture of dimyristoylphos-phatidylcholine and distearoylphosphatidylcholine. The fluorescence recovery after photobleaching (FRAP) technique was used to monitor the diffusion of both a lipid analog (N-(7-nitrobenzoxa-2,3-diazol-4-yl)-dimyristoylphosphatidyle thanolamine, NBD-DMPE) and fluorescein-labeled bacteriorhodopsin (Fl-BR). In the presence of bacteriorhodopsin, the mobile fractions of the two fluorescent probes display a shift of the percolation threshold toward lower temperatures (larger gel-phase fractions), independent of the protein concentration, from 43 degrees C (without bacteriorhodopsin) to 39 degrees C and 41 degrees C for NBD-DMPE and Fl-BR, respectively. Moreover, in the presence of bacteriorhodopsin, the gel-phase domains are much less efficient in restricting the diffusion of both probes than they are in the absence of the protein in the two-phase coexistence region. Bacteriorhodopsin itself, however, obstructs diffusion of NBD-DMPE and Fl-BR to about the same extent in the fluid phase of the two-phase region as it does in the homogeneous fluid phase. These observations suggest that 1) the protein induces the formation of much larger and/or more centrosymmetrical gel-phase domains than those formed in its absence, and 2) bacteriorhodopsin partitions almost equally between the coexisting fluid and gel phases. Although the molecular mechanisms involved are not clear, this phenomenon is fully consistent with the effect of the transmembrane peptide pOmpA of Escherichia coli investigated by electron spin resonance in the same lipid system.

Affinity Labels↗