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PubMed1976

Subunit symmetry of tetrameric phosphorylase a.

Native crystallographic data of tetrameric phosphorylase a crystals, space group P21, have been collected photographically to 3 A resolution. These data have been used in Patterson search methods in reciprocal and real space. The tetramers were found to exhibit molecular 222 symmetry. The cross vector between the centres of the two symmetry related tetramers in the unit cell was determined by two different translation function methods. On the basis of these rotation and translation function results a model for the arrangement of monomers within the tetramer and of tetramers in the unit cell is proposed; The 222 symmetry of the tetrameric molecule is found only when high resolution diffraction data are included (i.e. higher than 6 A). At lower resolution other symmetries dominate. Calculations with the proposed model have shown that these spurious symmetries result from the nonspecific overlap of protein-protein and solvent-solvent cross vectors. These results emphasize the importance of high resolution data when noncrystallographic symmetry of globular proteins is studied.

Chemical Phenomena↗
PubMed1983

Combined effect of restricted rotational diffusion plus jumps on nuclear magnetic resonance and fluorescence probes of aromatic ring motions in proteins.

A simple model is presented for the motion of phenylalanine and tyrosine rings in proteins. The model consists of restricted rotational diffusion of the rings about the side chain C alpha--C beta (chi 1) and C beta--C gamma (chi 2) axes combined with 180 degree ring flips. The model is used to evaluate order parameters for nuclear magnetic resonance relaxation and fluorescence depolarization probes of aromatic ring motions in proteins. The dependence of the order parameters on orientation in the ring plane is examined and it is demonstrated that in the presence of ring flips, additional ring librations can have a large effect on the probe order parameters.

Chemical Phenomena↗
PubMed1976

The O9 antigen of Escherichia coli. Structure of the polysaccharide chain.

The lipopolysaccharide from Escherichia coli O9:K30- was isolated in about 2% yield with aqueous 45% phenol at 65 degrees C, followed by ultracentrifugation. The polysaccharide moiety was obtained by graded hydrolysis and gel permeation chromatography. It consisted of a mannan which carried on its reducing end the core oligosaccharide of the R1 type. The mannan contained 1 leads to 2 and 1 leads to 3 linkages in a ratio of 3:2, as determined by methylation analysis and mass spectrometry. On periodate oxidation, 58% of the mannose residues were destroyed. Degradation of oligosaccharide mixtures with alpha-mannosidase from jack bean meal, as well as a specific rotation of [alpha]25D = +89 degrees indicated that all mannosyl linkages have the alpha-configuration. Smith degradation resulted in the liberation of mannosyl (1 leads to 3)-mannose (bound to glyceraldehyde), as established by methylation analysis. From these results we conclude that the O9 polysaccharide of E. coli has a pentasaccharide repeating unit of alpha-mannosyl(1 leads to 3)-alpha-mannosyl-(1 leads to 2)-alpha-mannosyl-(1 leads to 2)-alpha-mannosyl-(1 leads to 2)-mannose, which are joined in the polysaccharide through alpha-(1 leads to 3)-mannosyl linkages.

Chromatography, Gas↗
PubMed2005

Validity and limitation of manual rotational test to detect impaired visual-vestibular interaction due to cerebellar disorders.

The aim of this study was to investigate validity and limitation of the novel infrared system to record and analyze horizontal visual-vestibular interaction using whole-body rotation rapidly and conveniently in the routine vestibular clinic. We examined 11 patients with cerebellar dysequilibrium and 25 patients with peripheral dysequilibrium for vestibulo-ocular reflex in darkness (DVOR), visually-enhanced vestibulo-ocular reflex (VEVOR), and fixation suppression of vestibulo-ocular reflex (FSVOR), and compared the results with those of examination for head-fixed smooth pursuit and fixation suppression during caloric stimulation. The manual rotation stimuli were 0.5-0.75 Hz in frequency and 60-90 degrees /s in maximal angular velocity. Gain of vestibulo-ocular reflex in darkness was not significantly correlated with maximal slow phase velocity (MSPV) of caloric-induced nystagmus at that stimulus condition either in patients with peripheral dysequilibrium or in those with cerebellar dysequilibrium. An index for fixation suppression of vestibulo-ocular reflex during rotation stimulus was significantly lower in patients with cerebellar dysequilibrium than in normal control subjects and those with peripheral dysequilibrium. On the other hand, there was no significant difference among the two disease groups and the normal control group in gain of visually-enhanced vestibulo-ocular reflex. In about a half of patients with cerebellar dysequilibrium, measured smooth pursuit gain was lower than estimated smooth pursuit gain calculated based on a simple superposition theory of vestibulo-ocular reflex and smooth pursuit. Testing fixation suppression using the present system is an unusually convenient tool for detection of cerebellar dysequilibrium.

Cerebellum↗
PubMed1981

The lipopolysaccharide of escherichia coli C- studies on the anomeric configurations of the hexoses in the R1 core.

Lipopolysaccharide from E, coli C as well as lipopolysaccharides from submutants of E. coli with incomplete core structures in their lipopolysaccharides were isolated and quantitatively analyzed. Core oligosaccharides were isolated from lipopolysaccharides by acetic acid degradation and were purified by gel chromatography. The difference in molecular rotations of the core oligosaccharides from E. coli C and 6 submutants thereof with incomplete core structure were correlated to the differences in sugar compositions. The anomeric configurations have been deducted from the high or low contribution of each individual sugar to the molecular rotation of the core oligosaccharide from E. coli C. The primary structure of the hexose region of the lipopolysaccharide from E. coli C is primary structure of the hexose region of the lipopolysaccharide from E. coli C is, see formula in text. The anomeric configurations of glucoses I, II, and III were confirmed by precipitation reactions of alkali treated lipopolysaccharides from E. coli C, C23. 1, and C21 with Concanavalin A. The alpha-anomeric configurations of both the galactoses were confirmed by degradation studies with alpha-galactosidase (E.C.3.2.1.22) from green coffee beans with the isolated and purified core oligosaccharide from E. coli C71.

Carbohydrate Conformation↗
PubMed1985

Protein rotational diffusion measurements on the interaction of bee venom melittin with bacteriorhodopsin in lipid vesicles.

The rotational diffusion of bacteriorhodopsin reconstituted into dimyristoylphosphatidylcholine vesicles was measured by the technique of flash-induced transient dichroism. In the presence of melittin, a cell lysing peptide from honey bee (Apis mellifera) venom, dose-dependent loss of rotational mobility was observed. Chemically modified melittin derivatives, in which free amine groups were either acetylated or succinylated, were impaired in their ability to induce immobilisation of bacteriorhodopsin. Bacteriorhodopsin reconstitutions of differing lipid/protein ratio were tested and it was found that the bacteriorhodopsin immobilisation phenomena depended on the melittin/protein ratio, not the melittin/lipid ratio. This suggests that melittin produces its effect via direct interaction with bacteriorhodopsin. A mechanism is proposed in which the aggregation of bacteriorhodopsin is induced by electrostatic attraction between its anionic surface moieties and the highly cationic C-terminal segment of melittin.

Acetylation↗
PubMed1989

Slow-motion ESR study of order and dynamics in oriented lipid multibilayers: effects of unsaturation and hydration.

Electron spin resonance (ESR) experiments were carried out on 3-doxyl-5 alpha-cholestane spin-label (CSL) molecules embedded in macroscopically oriented multibilayers of dimyristoylphosphatidylcholine (DMPC), palmitoyloleoylphosphatidylcholine (POPC), dioleoylphosphatidylcholine (DOPC) and dilinoleoylphosphatidylcholine (DLPC). For these lipids we studied the effects of temperature, hydration and unsaturation on the orientational order parameters and rotational motions of the probe molecules in the liquid crystalline phase. The experimental ESR spectra were simulated by a numerical solution of the stochastic Liouville equation (SLE) for the density matrix of a spin-label molecule. This allows extraction of detailed information about both molecular order and rotational dynamics. The data show that, in our temperature range, the lipid systems are in the slow-motion regime, thereby precluding a motional narrowing interpretation. This is illustrated by a simple model calculation which shows that a fast-motion interpretation seriously overestimates the order parameters. We have compared our results with data obtained independently from angle-resolved fluorescence depolarization (AFD) experiments on oriented bilayers in which 1-[4-(trimethylammonio)phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH) molecules were used as fluorescent probes (Deinum et al., (1988) Biochemistry 27, 852-860). It is found that the orientational order and the rotational dynamics obtained with both techniques agree well. This shows that the probe molecules do not perturb the local bilayer structure to any large extent and that they indeed reflect the intrinsic behaviour of the lipid molecules. Upon increase in temperature or hydration, we observe faster reorientational motion and lower molecular ordering. In contrast, we do not find any systematic effect of unsaturation on molecular reorientational motion. Our results indicate that changes in membrane molecular order and reorientational dynamics have to be considered separately and are not necessarily correlated as implied by the common concept of membrane fluidity.

Electron Spin Resonance Spectroscopy↗
PubMed1994

Three-dimensional illusory objects produced by rotation in depth.

Rotation of a Kanizsa triangle in depth around its vertical axis causes a perception of a three-dimensional object with a flat, rigid illusory triangle between the inducing discs. When the inducing discs of a Kanizsa triangle were made thicker, the illusory triangle between the discs also became thicker. In the experiments both computer animation and real inducers made of plastic were used. The method promoted border perception in a three-dimensional illusory figure. We suggest that the perception of three-dimensional illusory objects is due to a process which is also used in the perception of real three-dimensional objects.

Adult↗
PubMedDate not supplied

Chemical geometrodynamics: physical fields can cause asymmetric synthesis.

This paper presents theoretical arguments that suggest that chiral combinations of physical fields which can induce motion of elementary particles or molecular systems can in principle cause asymmetric synthesis. The theory is founded on the application of parity and time reversal operators to chiral dynamical systems. The motion of these systems induced by a chiral set of physical fields is shown not to be invariant on parity and time reflection. The relationship between tetrahedral dissymmetry and helical dissymmetry is analyzed in terms of the moments of inertia of a tetrahedrally dissymmetric rotor rotating around each of the four bond axes. The magnitude of anticipated enantiomeric excess which would result from conducting a prochiral chemical reaction in a chiral set of physical fields is estimated to be very small, parts per million or less, for virtually all sets of readily accessible physical fields. The results of experiments in which prochiral chemical reactions were conducted in a sealed tube which was spinning perpendicular or parallel to the earth's surface, are reviewed as are experiments in which prochiral chemical reactions were conducted in intense oriented magnetic fields. Enantiomeric recognition may have been one of the principal mechanisms for amplifying small differences in the rates of a given prochiral chemical reaction.

Chemical Phenomena↗
PubMed2006

Relationship between spatial abilities, mental rotation and functional anatomy learning.

This study investigated the relationship between visuo-spatial representation, mental rotation (MR) and functional anatomy examination results. A total of 184 students completed the Group Embedded Figures Test (GEFT), Mental Rotation Test (MRT) and Gordon Test of Visual Imagery Control. The time spent on personal assignment was also considered. Men were found to score better than women on both GEFT and MRT, but the gender effect was limited to the interaction with MRT ability in the anatomy learning process. Significant correlations were found between visuo-spatial, MR abilities, and anatomy examination results. Data resulting from the best students' analyzes underscore the effect of high MR ability which may be considered reliable predictor of success in learning anatomy. The use of specific tests during learning sessions may facilitate the acquisition of anatomical knowledge.

Adolescent↗
PubMedDate not supplied

Local mechanisms for the separation of optic flow-field components in the land crab, Cardisoma guanhumi: a role for motion parallax?

Although a number of global mechanisms have been proposed over the years that explain how crabs might separate the rotational and translational components of their optic flow field, there has been no evidence to date that local mechanisms such as motion parallax are used in this separation. We describe here a study that takes advantage of a recently developed suite of computer-generated visual stimuli that creates a three-dimensional world surrounding the crab in which we can simulate translational and rotational optic flow. We show that, while motion parallax is not the only mechanism used in flow-field separation, it does play a role in the recognition of translational optic flow fields in that, under conditions of low overall light intensity and low contrast ratio when crabs find the distinction between rotation and translation harder, smaller eye movements occur in response to translation when motion parallax cues are present than when they are absent. Thus, motion parallax is one of many cues that crabs use to separate rotational and translational optic flow by showing compensatory eye movements to only the former.

Adaptation, Physiological↗
PubMed1984

The capacity of basic peptides to trigger exocytosis from mast cells correlates with their capacity to immobilize band 3 proteins in erythrocyte membranes.

The effect of mast-cell-triggering peptides on the rotational properties of band 3, a protein component of the human erythrocyte membrane, was measured by observing flash-induced transient dichroism of the triplet probe eosin maleimide. In the presence of melittin, polylysine and five synthetic peptides, varying degrees of retardation in the rotational motion of band 3 were produced. When placed in order of band 3 immobilizing activity, the peptides formed a series identical with their order of efficacy in releasing 5-hydroxytryptamine from rat peritoneal mast cells. The correspondence in the abilities to immobilize band 3 in the erythrocyte and trigger mast cells is significant because structure-activity analyses of the peptides show both processes to have the same cationic, hydrophobic and stereochemical requirements. Probably, the immobilization of band 3 proteins reflects an ability of the basic peptides to aggregate anionic surface moieties, and therefore a similar mechanism is implied in mast-cell triggering.

Animals↗
PubMedDate not supplied

Millimetric cover test--a linear strabismometric technique.

In ten normal subjects we measured the angular rotations of the globe, both in adduction and in abduction, corresponding to limbus shifts from 1 to 7 mm. Our study demonstrated that to each millimeter of temporal limbus shift corresponds an average adduction of about 4.6 degrees and to each millimeter of nasal limbus shift an average abduction of about 4.8 degrees. These experimental results give a sound foundation to the clinical evaluation of the strabismic angle by measuring, with a millimeter ruler, the limbus shift of the nonfixating eye by assuming fixation. This technique appears particularly useful as a substitute for the simultaneous prism and cover test, in the evaluation of a squint with a variable angle, and in measurements in other positions of gaze.

Adolescent↗
PubMed1982

Dynamics of erabutoxin b as studied by nuclear magnetic resonance. Relaxation studies of methyl proton resonances.

Longitudinal and transverse relaxation times were measured for well-resolved and assigned methyl proton resonances of erabutoxin b at 270 MHz, 300 MHz and 500 MHz. Both longitudinal and transverse magnetization decay curves are non-exponential due to cross-relaxation and cross-correlation effects. The longitudinal and transverse relaxation rates were obtained from the initial slope of both magnetization decay curves. The correlation times for the isotropic tumbling motion of the protein were determined to be 2.82 ns at 300 K and 1.62 ns at 330 K from the analysis of the relaxation data of some alpha protons. Using these values, the relaxation data of methyl protons were fitted to various theoretical models. Most of the methyl resonances could be fitted well to a model which allowed methyl rotation (in the range 0.01-0.05 ns) and an external contribution from protons assumed to be in positions derived from X-ray coordinates. The data for a few methyl groups, however, could not be fitted in this way. For these a smaller number of external protons than predicted by the X-ray coordinates was assumed. Additionally, a larger amplitude motion had to be introduced into the model for particular residues. This additional motion requires concerted protein motion close to these residues, since the X-ray structure suggests that steric hindrance would prevent local motion. These results are consistent with the idea of a flexible and dynamic structure for proteins.

Elapid Venoms↗
PubMed1989

Correlation between internal motion and emission kinetics of tryptophan residues in proteins.

Time-resolved fluorescence anisotropy measurements of tryptophan residues were carried out for 44 proteins. Internal rotational motion with a sub-nanosecond correlation time (0.9 +/- 0.6 ns at 10 degrees C) was seen in a large number of proteins, though its amplitude varied from protein to protein. It was found that tryptophan residues which were almost fixed within a protein had either a long (greater than 4 ns) or short (less than 2 ns) fluorescence lifetime, whereas a residue undergoing a large internal motion had an intermediate lifetime (1.5-3 ns). It is suggested that the emission kinetics of a tryptophan residue is coupled with its internal motion. In particular, an immobile tryptophan residue emitting at long wavelength was characterized by a long lifetime (greater than 4 ns). It appears that a tryptophan residue fixed in a polar region has little chance of being quenched by neighboring groups.

Fluorescence Polarization↗
PubMed1985

Segmental flexibility of the C1q subcomponent of human complement and its possible role in the immune response.

Fluorescence polarization techniques were used to study the rotational dynamics of the C1q subcomponent of human complement. C1q was covalently labeled with dansyl (DNS) chloride. Digestion of either C1q-DNS4.0 or C1q-DNS1.8 conjugates with pepsin showed that about 75% of the DNS probes were attached to the C1q globular heads and that the remainder were on the collagen-like stalk (peptic fragment). C1q-DNS conjugates readily agglutinated IgG-coated latex beads and combined with C1r2C1s2 to form hemolytically active 16 S C1-DNS. Both C1q-DNS and C1-DNS samples displayed steady-state rotational correlation time and fluorescence lifetime transitions near 48 degrees C. Hydrodynamic studies showed that C1q formed soluble aggregates near the transition temperature. In contrast, stalk samples with a DNS probe apparently attached to the large central fibril showed no thermal transitions or aggregation even when heated above 50 degrees C. Nanosecond fluorescence depolarization measurements detected restricted flexible motions of the C1q heads with an associated rotational correlation time, phi s, of about 25 ns. The C1q anisotropy decay was dominated, however, by a long component, phi L, of perhaps 1000 ns. Except for probe wiggle, the stalk-DNS anisotropy profile was essentially flat. The rapid rotations associated with phi s could represent restricted twisting motions of the arm-head segments or wobbling motions of the heads themselves. Such motions may facilitate binding of the C1q heads to immune complexes. Straightforward diffusion calculations indicated that phi L could represent either global tumbling of the entire C1q molecule or wagging motions of the individual arm-head segments, as suggested by electron micrographs. Upon binding of the C1q heads to an activator, some of the C1q segments may be held in a slightly more open or more closed conformation, which in turn may trigger activation of the C1 proenzymes. In conclusion, we suggest a plausible triggering mechanism for C1 activation that is compatible with the flexible properties of its subcomponents.

Complement Activating Enzymes↗
PubMed1975

A quantitative test of optokinetic nystagmus and its data processing by computer.

A quantitative test of optokinetic nystagmus was proposed. Horizontal nystagmus was examined by a large rotating cylinder with vertical stripes. Nystagmus responding to the cylinder rotation with an acceleration of 2 degrees/sec2 for 90 seconds was recorded with an electronystagmograph. On the records, the number of beats, average eye-speed, and average amplitude per each 10 seconds were calculated. This method was suitable for testing the nature of optokinetic nystagmus which indicates the ability of the eyes to adapt to objects moving through the visual field. Moreover, in order to save trouble in hand-scoring of each parameter of nystagmus, computer processing of electronystagmographic data was introduced. The results were printed numerically on the teletypewriter, and displayed graphically on a cathode ray tube and X-Y recorder. By displaying measured values on the form already printed with the normal ranges, the evaluation of the results was performed readily and objectively.

Adolescent↗
PubMed1975

Self-association of the major protein component of bovine serum high density lipoprotein.

The major protein component of bovine high density lipoprotein was investigated in solution by fluorescence polarization and ultracentrifugal techniques. A fluorescent derivative of this protein with 1-dimethylaminonaphthalene-5-sulfonyl chloride was employed in the fluorescence experiments. Over the concentration range from 5-10(-7) M to 5-10(-4) M of the protein monomer at pH values from 2 to 11 and ionic strengths from 0.03 to 2.0, at 23 degrees C, the major protein of bovine high density lipoproteinapoprotein (Apo-HOL-I) was found to exist in a stable aggregated form. The aggregate was not affected by dioxane additions of up to 20% nor by Triton X-100 to 0.2%, but dissociated readily in the presence of 0.07% sodium dodecylsulfate or 6 M urea. At concentrations below 5-10(-7) M, dissociation of the protein aggregate started spontaneously and continued down to 10(-8) M, the lowest measurable concentration. Several physiocochemical properties of the major protein of bovine high density lipoprotein were determined in the stable aggregate form. Molecular weight was 104 000 from ultracentrifugal analysis and 80 000 from gel-filtration. Rotational relaxation time was 115 ns at 25 degrees C, and s-0 20,w was 4.78 s. The results suggest very strong protein-protein interactions (Kd less than 10(-7) M) that are not electrostatic in nature. Hydrophobic interactions of a magnitude that could be affected by 20% dioxane or 0.2% Triton X-100 detergent are also excluded. There is saturation of the interaction sites by the aggregation of a few protein monomer units possibly to form a tetramer which is moderately asymmetric (1:4 axial ratio, assuming an ellipsoid of revolution) and relatively rigid. The strong protein-protein interactions in this pure apolipoprotein suggest the possibility of competition of inter-protein associations with protein-lipid interactions in in vitro lipid binding or lipoprotein reconstitution experiments.

Animals↗