Non-random Orientation Research Articles

Pattern photobleaching of fluorescent lipid vesicles using polarized laser light

A burst of linearly polarized laser radiation incident on a spherical lipid vesicle, liposome, or biological cell can produce a well-defined nonuniform distribution of membrane-bound fluorescent molecules, provided the absorption transition dipole moment of the fluorescent label has a nonrandom orientation relative to the membrane surface and can be photobleached by the laser radiation. The return (recovery) of fluorescent membrane-bound molecules to a uniform distribution can be monitored using the same polarized radiation source. Under appropriate conditions this recovery is characterized by a single exponential time constant tau. This time constant is related to the radius R of the vesicle and the lateral diffusion coefficient D of the fluorescent membrane-bound molecules by the equation R2 = 6D tau. In the case of vesicle membranes this result is not limited by diffraction and so should be applicable to vesicles whose radii are less than the wavelength of light. The above considerations are illustrated by the polarized light photobleaching-recovery of lipid vesicles containing a fluorescent lipid, N-4-nitro-benzo-2-oxa,1,3-diazole l-alpha-dimyristoylphosphatidylethanolamine (NBD-DMPE).

Heat Exchange Influence on Foraging Behavior of Zonotrichia Flocks

The heat exchange of individuals in a foraging mixed population of Zonotrichia leucophrys and Z. atricapilla in western Oregon is analyzed for its influence on the direction of stance and feeding location. Values for heat gain or loss in the field were generated from a model that estimates the equivalent blackbody temperature (Te) and from previous laboratory findings for the effects of air temperature, solar radiation, and wind speed on metabolism. Observations were recorded at 1—min intervals throughout the daylight hours with samples at weekly intervals from January to March 1978. A summation of 1500 observations on direction of stance subjected to a g test for randomness supports the hypothesis that spatial orientation of individuals is not random. Maximum differences in Te for different stances with respect to the wind direction were only 1°C because of the low winter values for incoming shortwave radiation. More important factors than heat exchange influencing the direction of stance were food availability, social interactions, and the location of the hedge in the area used for cover. Placing a trace line of food perpendicular to the most frequently observed direction of stance caused a significant change in percentage of time spent facing each direction for that location. Individuals were facing the same direction as the majority of their neighbors within a 2—m radius during 68% of the total number of recorded observations for a nonrandom flock orientation. Heat loss was affected by changes in the microhabitats at the site. Differences in wind speed, air temperature, and solar radiation were large enough to increase metabolic rate as much as 20% for the open area foraging as compared to the hedge. Instead of feeding in the open area during midday where the shortwave radiation is greatest, the flock would often move into the hedge, thus occupying each location when the thermal conditions were least advantageous. Factors that may influence this feeding behavior could be a decreased cost—to—gain ratio for caloric intake in the open area in conjunction with circadian rhythms for metabolic rate and energy needs.

Progressive development of quartz fabrics in a shear zone from Monte Mucrone, Sesia-Lanzo Zone, Italian Alps

Quartz c-axis fabrics are described from a shear zone in a jadeite — garnet bearing meta-granite from Monte Mucrone, in the Sesia-Lanzo Zone of the western Italian Alps. Quartz blebs in the meta-granitoid are progressively deformed into cigar shaped lenses, and are recrystallized. Fabrics measured from individual blebs show considerable variation resulting from an initial orientation effect, and are not very enlightening. A synoptic diagram, however, has a pole-free area which can be correlated with the extension direction, and an asymmetry which is consistent with the known sense of shear operating in the zone. Although the technique of preparing synoptic diagrams is rather painstaking, its use is advocated for complex fabric situations, as it may allow partial removal of problems associated with non-random initial orientation distributions.

Thermal Stress of the Orb-Weaving Spider Argiope Trifasciata (Araneae)

The influence of thermal stress on the population dynamics of Argiope trifasciata ForskAl, a diurnal orb-weaving spider, was studied in the southeastern United States. Comparison of laboratory determined thermal tolerances (48.90C to 58.60C for second through tenth instars) and spider body temperatures modeled under field conditions in 1975 indicated that A. trifasciata did not experience mortality from thermal overloading. Vertical orientation of spiders on their webs exposed the minimum body area of the spider to direct solar insolation during mid-day. This orientation and silver body coloration probably helped reduce body temperatures below lethal temperatures. A behavioral correlate of sublethal stress, non-random web orientation, was exhibited on 1 Aug and 14 Aug by spiders occupying all types of habitats. This is the time period when spider body temperatures were closest to laboratory-determined thermal tolerance maxima. Web orientations at these times exposed less surface area of the spiders to the sun. Web orientations became non-random again in Oct, this time resulting in maximum exposure of the spiders to the sun. The venter (underside of the abdomen) changed with maturity morphologically from silver to black, and was oriented toward the sun (SW to SE).

Organisation in the Structure of the Cytoplasmic Ground Substance

Most types of cells are known from their structure and overall form to possess a characteristic organization. In some instances this is evident in the non-random disposition of organelles and such system subunits as cisternae of the endoplasmic reticulum or the Golgi complex. In others it appears in the distribution and orientation of cytoplasmic fibrils. And in yet others the organization finds expression in the non-random distribution and orientation of microtubules, especially as found in highly anisometric cells and cell processes. The impression is unavoidable that in none of these cases is the organization achieved without the involvement of the cytoplasmic ground substance (CGS) or matrix. This impression is based on the fact that a matrix is present and that in all instances these formed structures, whether membranelimited or filamentous, are suspended in it. In some well-known instances, as in arrays of microtubules which make up axonemes and axostyles, the matrix resolves itself into bridges (and spokes) between the microtubules, bridges which are in some cases very regularly disposed and uniform in size (Mcintosh, 1973; Bloodgood and Miller, 1974; Warner and Satir, 1974).

Late Nagssugtoqidian stress rientation derived from deformed granodiorite dykes north of Holsteinsborg, West Greenland

A suite of granodiorite dykes, of varied but non-random orientation, cuts basement gneisses in a 15 km x 8 km coastal strip around lat. 67°N in central West Greenland. The dykes which were metamorphosed in the granulite facies have been deformed by simple shear and vary from apparently unstrained to highly strained. The deformation occurred during a late stage of Nagssugtoqidian deformation (Lower Proterozoic). The orientation of the principal stress planes and of the σ 1 axis are determined on a best-fit basis from the change in sense of shear direction observed in the horizontal and in the vertical plane. The positions of the σ 2 and σ 3 axes are determined by a method involving a comparison of the observed shear directions with those predicted from a model stress system with known σ 1 and σ 2 = σ 3 . This stress model gives a σ 1 with a plunge of 28° on a bearing of 161°, a horizontal σ 3 and a steep σ 2 . This result is consistent with other more approximate estimates of the Nagssugtoqidian stress orientation near the Nagssugtoqidian front in W Greenland.

Oriented adsorption of purple membrane to cationic surfaces.

We have investigated the orientation of isolated fragments of Halobacterium halobium purple membrane (PM) adsorbed to poly-L-lysine-treated glass (PL-glass), by quanitative electron microscopy. Three lines of evidence support the conclusion that the cytoplasmic side of the membrane is preferentially absorbed. First, monolayer freeze-fracture reveals nonrandom orientation; more fracture faces (89%) are particulate than smooth. Second, the amount of each membrane surface present can be assayed using polycationic ferritin; 90% of all adsorbed membrane fragments are labeled. Third, it is possible to distinguish two surfaces, "cracked" (the extracellular surface) and "pitted" (the cytoplasmic surface) , in slowly air-dried, platinum-carbon-shadowed membranes. When applied under standard conditions, more than 80% appear cracked. Selection for the cytoplasmic by the cationic substrate suggests that the isolated PM, buffered at pH 7.4 and in the light, has a higher negative charge on its cytoplasmic surface than on its extracellular surface. Nevertheless, cationic ferritin (CF) preferentially adsorbs to the extracellular surface. Orientation provides a striking example of biomembrane surface asymmetry as well as the means to examine the chemical reactivity and physical properties of surfaces of a purified, nonvesicular membrane fragment.

Orientation of Giemsa C-bands in interphase cells of Allium cepa L.

Orientation of Giemsa C-bands in Allium cepa was studied in both mitotic and interphase cells. It has been shown that telophase orientation of the chromosome is maintained throughout the interphase and early phophase. It has been assumed that this non-random orientation is due to anchorage of the telomeres with the nuclear membrane. Contrary to earlier observations, 2 by 2 pairing of the telomers could not be traced to this species.

The contouring of orientation data represented in spherical projection

The inadequacy of the current method of contouring orientation data in terms of the concentration of points occurring in 1% of the projected area is demonstrated. In particular, the maximum concentration and the areas occupied by the different concentrations are shown to be dependent on sample size. Using a counting area of 100/n% of the projection, where n is the sample size, yields meaningful orientation patterns which are comparable for different sample sizes. This is illustrated with reference to computer generated random and non-random orientation patterns. The data obtained are compared with predicted values and form a basis for comparison with measured orientation patterns to test their significance.

Nonrandom Orientation of Entrance Holes to Woodpecker Nests in Aspen Trees

Nonrandom Orientation of Entrance Holes to Woodpecker Nests in Aspen Trees

Proton NMR of the protected tetrapeptides TFA-Gly-Gly- l- X- l-Ala-OCH 3, where X stands for One of the 20 common amino acids

The 1H NMR parameters for the 20 common amino acid residues have been measured in the protected linear peptides TFA-Gly(1)-Gly(2)- l- X(3)- l-Ala(4)OCH 3 in d 6-DSMO solution. In view of their potential use as “random coil” NMR parameters for studies of peptide conformations in DSMO solutions, these data were further qualified by investigations of the molecular conformations of the tetrapeptides. 1H, 13C, and 19F NMR were all consistent with a predominantly extended flexible random coil form of the peptide backbone. Correspondingly, the amino acid sequence effects are small, i.e., the NMR parameters of Gly(1), Gly(2), and Ala(4) were found to be only little affected by the difference in residue X(3). On the other hand there is evidence for a nonrandom spatial orientation of bulky side chains of X in these peptides.

The scattering of light from systems with nonrandom orientation correlations

Theories for calculating the scattering of light from solid polymeric materials can be divided into two classes. The particle scattering theories using models of the scattering entities and treating the total scattering in a “dilute solution” approximation form one of these. The statistical theories utilizing correlation functions constitute the other class. They are better in principle but cannot be easily connected with the known physical structure of the material. Moreover, the existing theories are either too simple or too complicated to be of practical use. In the present article a new theory is developed which takes the correlation function approach, but in such a way that the resulting expressions can be applied to obtain meaningful parameters from experimental data. The derivation is accomplished by expansion of the general correlation function G(r) into a series of spherical harmonics and introducing a number of rather general assumptions. It is also pointed out that cross correlations are intractable. This new theory is particularly suited to compare the two types of light scattering theories as applied to macroscopically isotropic materials. It also shows that the determination of the usual scattering components is not enough to obtain the maximum amount of information possible.

Scattering of light by films having nonrandom orientation fluctuations. II

AbstractThe theory for scattering of light from films in which the orientation correlation between two scattering elements depends upon the angle β between the optic axes and the vector connecting the two elements is extended. A delta‐function type dependence is assumed in which the correlation is strongest when β equals some preferred value β0. Calculated results of scattered intensities are shown to be similar to experimental observations.

The Specification of Order in Mesophases

The description of order in mesophases in terms of angularly dependent radial distribution functions and in terms of correlation functions in density and oreientation is discussed. The determination of these functions from light scattering and diffraction data is described. The concept of non-randomness of orientation correlations is introduced and its description in terms of non-randomness parameters or correlation functions isn proposed. It is pointed out that mesophases of complex structure may be defined in terms of parameters describing the amplitudes and correlation distances for the correlations in density and in random and non-random orientation. The most striking chages at mesophase transitions are in the randomness of the orientation correlations. The relationship between the correlation functions and the morphology for model systems is illustrated.

A transition state model for active transport

A transition state model of simultaneous chemical reaction and diffusion in anisotropic systems is developed. In this model the anisotropy is reflected in a non-random orientation of the reaction co-ordinates. Direct local coupling of the two processes emerges. The expected magnitude of the effect is discussed. A fundamental difficulty is discussed which points out that the direct coupling coefficients have no influence on the distribution of chemical species, but the coupling coefficients do contribute to the entropy production. Also, that part of the reaction rate caused by coupling is balanced by the diffusion flow caused by coupling.

Effect of Nonrandom Polymer Chain Orientation in the Thickness Direction on Infrared Absorption Measurements

Effect of Nonrandom Polymer Chain Orientation in the Thickness Direction on Infrared Absorption Measurements

Light scattering by liquid crystals

The scattering of light by liquid crystals is primarily a result of orientation fluctuations and is formally similar to the scattering by solid crystalline polymers. Some experimental results for the photographic scattering of mesophases of cholesteryl myristate are presented. The patterns for the cholesteric state are similar to those for spherulitic polymers and are analyzed using the theory for scattering from media exhibiting nonrandom orientation correlations. As a result of the light scattering studies it may be shown that the cholesteric state is characterized by disc-like correlations, while the smectic state and solid cholesteryl myristate both show random orientation correlations.

Some theoretical considerations of polarized light effects on unoriented biological systems

Macromolecules, viruses, and cells may be anisotropic with regard to light absorption in part or the whole of their structures. Anisotropies could arise as a result of a regular non-random orientation or coiling of ultraviolet-absorbing macromolecules such as DNA, RNA or protein within the organism. For example, oriented parallel fibers of DNA are known to be anisotropic at 260 mμ due to the regular orientation of the ultraviolet-absorbing purines and pyrimidines. If there is only one anisotropic part of an organism, the anisotropy may be masked by isotropic absorption in other components and may not be detected by absorption measurements with polarized light. An absorption anisotropy in an ultraviolet sensitive component could be resolved as an inactivation anisotropy for the organism (or molecule) if one were to study the biological effects of incident polarized ultraviolet. One need only make the reasonable assumption that the quantum yield for the biological effect is the same for all absorbed energy of a given wavelength and that the more energy is absorbed, the greater the biological effect. Hence incident polarized light may have a greater or less effectiveness for a given biological alteration, depending on the direction of the electric vector with regard to some axis of the organism. Although alignment of organisms would be preferred to implement this idea, many organisms of interest cannot be easily aligned. In this paper, we explore the possibilities for detecting such inactivation anisotropies by the polarized ultraviolet irradiation of an unoriented stationary collection of units. If the organisms are assumed to be randomly oriented in three dimensions but held stationary during irradiation, differences between polarized light and unpolarized fight survival curves are theoretically expected. However, the magnitude of the differences is so small as to make experimental resolution improbable with anything except unreasonably large dichroic ratios. If one axis of the organism is constrained to stay fixed in a plane, then the possibility of experimentally resolving an anisotropy is considerably improved. For dichroic ratios less than one, the best resolution is obtained from a comparison of the survival curve for the electric vector parallel to the plane of the organism axes to the survival curve for the electric vector perpendicular to that plane. For dichroic ratios > 1, the best resolution is obtained from a comparison of the survival curve for unpolarized light incident perpendicular to the plane to that for polarized light with the electric vector perpendicular to the plane. For dichroic ratios to be expected from some DNA configurations, it seems possible that this resolution is good enough to detect inactivation anisotropies.

Scattering of Light by Films Having Nonrandom Orientation Fluctuations

A theory is developed for the scattering of light by a two-dimensional solid having correlated fluctuations in density and in the optic axis orientation of anisotropic scattering elements. The case of nonrandom orientation correlations is considered where the probability of a given angle between two optic axes depends upon the separation of the scattering elements r and the angle β which the optic axis makes with the interconnecting vector. It is shown that in addition to the density correlation function γ(r), three correlation functions T0(r), [T2(r) − S2(r)], and [T4(r) − S4(r)] are usually sufficient to describe the orientation correlations. The values of the latter two characterize the kind and amount of dependence of the scattered intensity upon the polarization directions ψ1 of the incident and ψ2 of the scattered light, while the dependence of these functions upon r characterizes the dependence of scattered intensity upon the angle θ between the incident and scattered beam.

Determination of latex particle size by light scattering. V. Polarization ratio at 90°

Unpolarized incident light was used to determine the polarization ratio, ρ u , for a series of polystyrene and butadienestyrene latices. The experimentally observed ρ u 'S were found to differ appreciably from those predicted by Mie theory. The discrepancy is shown to be due to inherent anisotropy of the latex particles, and this conclusion is confirmed by a study of the polarization ratios with vertically and horizontally polarized incident light. This presence of anisotropy makes uncertain the determination of the particle size of latex from ρ u measurements at 90° by use of Mie theory. Since latex particles are spherical, the anisotropy is believed to arise from nonrandom orientation of polymer chains in the colloidal latex particles.