Understanding the Impact of Oligomeric Polystyrene Side Chain Arrangement on the All‐Polymer Solar Cell Performance

The introduction of oligomeric polystyrene (PS) side chains into the conjugated backbone is proven to enhance the processability and electronic properties of semiconducting polymers. Here, two series of donor and acceptor polymers are prepared with different molar percentages of PS side chains to elucidate the effect of their substitution arrangement on the all‐polymer solar cell performance. The observed device performance is lower when the PS side chains are substituted on the donor polymer and higher when on the acceptor polymer, indicating a clear arrangement effect of the PS side chain. The incorporation of PS side chains to the acceptor polymer contributes to the decrease in phase separation domain size in the blend films. However, the reduced domain size was still an order of magnitude larger than the typical exciton diffusion length. A detailed morphological study together with the estimation of solubility parameter of the pristine PS, donor, and acceptor polymers reveals that the relative value of solubility parameter of each component dominantly contributes to the purity of the phase separated domain, which strongly impacts the amount of generated photocurrent and overall solar cell performance. This study provides an understanding of the design strategies to improve the all‐polymer solar cells.     

l-cysteine-induced fabrication of spherical titania nanoparticles within poly(ether-imide) matrix

In the presented study, a new l-cysteine-containing diamine is synthesized and fully characterized and its application for the in situ sol–gel fabrication of poly(ether-imide)/titania nano hybrid materials is investigated. The electron microscopic photographs (TEM, FE-SEM and AFM) of the resulted materials confirm the production of spherical nanoparticles with well dispersion and narrow particle size distribution which is a usual challenge in the sol–gel methods. In addition to the positive effects on the particles morphology, the existence of amino acid containing pendant groups in the structure of polymer chains led to the comprehensive interaction with titania phase. As a result, the improvement in the flexibility of polymer backbone (as one of the most serious difficulties in polyimides processing) is obtained while its thermal stability dose is not sacrificed (confirmed by TGA and DSC techniques).     

The effect of (2-chloroethyl)trimethylammonium chloride (CCC) and gibberellic acid on the growth and development of wheat cultivated under red or blue light

The effect of CCC and GA₃ on the growth and development of spring wheat (Triticum aestivum L.) cultivated under predominantly red (500–700 nm) or blue (400–500 nm) light was investigated. Red light enhanced the development of wheat during the exponential phase of growth. This effect presumably implicated the promotion of gibberellin synthesis under red light. The strong inhibitory action of CCC under red light (the inhibition was lower under blue light) might be interpreted in a similar way. The growth became more intensive under blue light after caring and was accompanied by increased susceptibility to giberellic acid treatment.     

Affinity-specific protein separations using ligand-coupled particles in aqueous two-phase systems: I. Process concept and enzyme binding studies for pyruvate kinase and alcohol dehydrogenase from Saccharomyces cerevisiae

A process using ligand-coupled particles in aqueous polyethylene glycol-dextran two-phase polymer systems was developed to achieve a highly selective, scaleable biochemical separation process. Product protein is bound to the ligand-coupled particles that quantitatively distribute to the polyethylene glycol-rich upper phase. Other proteins and contaminants partition preferentially to the dextran-rich lower phase.The process offers significant advantages over affinity partitioning here the ligand is coupled to the backbone of a polyethylene glycol polymer. These advantages include a much wider diversity of ligands that can be coupled to particles and more effective confinement of the ligand in the process. Affinity partition with ligands coupled to particles is more amenable to scale-up than is affinity chromatography. A variety of commercially available Sepharose-based particles are suitable for this process. Homogenates from Saccharomyces cerevisiae, which is genetically altered to overproduce pyruvate kinase, and Cibacron blue F3G-A-coupled Sepharose particles are used as a model system for the process. Binding studies with/without aqueous two-phase systems show that the formation of a two-phase system after the adsorption equilibrium is reached does not affect the apparent dissociation constant. Binding of protein to ligand-coupled particles is more rapid in single-phase systems than in the polymer two-phase system. Single-phase binding eliminates the mass transfer resistance associated with redistribution of product protein from the dextran-rich bottom phase to the polyethylene glycol-rich top phase.     

RNA and protein metabolism in the particulate fractions of the gametophytes of bracken fern during growth in red and blue light

Summary The metabolism of RNA and protein in the gametophytes of bracken fern (Pteridium aquilinum) is affected by the quality of light in which they are grown. When sporelings were grown as two-dimensional gametophytes in blue light, particulate fractions separated from the sporelings exhibited greater incorporation of uridine-³H and leucine-³H into RNA and protein, respectively, than those from sporelings grown as one-dimensional protonema in red light. After various periods of exposure of gametophytes to red or blue light in the presence of uridine-³H, the nuclei-rich fraction showed the highest specific activity in RNA, and irrespective of incubation time, blue light was more effective than red light. The possibility that enhanced synthesis of RNA in the nucleus in response to blue light is significantly related to the morphological growth pattern of the gametophytes, is discussed.     

Stomatal Responses to Light and Drought Stress in Variegated Leaves of Hedera helix

Direct and indirect mechanisms underlying the light response of stomata were studied in variegated leaves of the juvenile phase of Hedera helix L. Dose response curves of leaf conductance were measured with blue and red light in leaves kept in normal or in an inverted position. In the green portions of the leaves, the sensitivity to blue light was nearly 100 times higher than that to red light. No response to red light was observed in the white portions of the leaves up to 90 micromoles per square meter per second. Red light indirectly affected leaf conductance while blue light had a direct effect. Leaf conductance was found to be more sensitive to drought stress and showed a more persistent aftereffect in the white portions of the leaves. A differential effect of drought stress on the responses to blue and red light was also observed.     

Azobenzene-modified poly(l-glutamic acid) (AZOPLGA): its conformational and photodynamic properties

Azobenzene-modified poly(l-glutamic acid) (AZOPLGA) polymers with 22 and 35 mol % of azo chromophores in the side chains have been synthesized by condensing 4-methoxy-4'-aminoazobenzene and poly(l-glutamic acid). These polymers have been characterized by NMR, FT-IR, and UV-visible spectroscopic techniques. The conformational features of the polymer backbone chains in the films that were cast from the polymer solutions prepared in different solvents have been investigated by circular dichroism spectroscopy. Experimental data suggested that the thermal cis-trans relaxation and photoinduced birefringence, which are related to the azo chromophores in the side chains of polymer, are not affected by the conformations of polymer backbones. However, the modulations of the surface relief gratings, the result of photoinduced mass transport process, recorded on these polymers are sensitive to polymer main chain conformation, as well as the degree of functionalization.     

不同波长光照对罗汉果光合及生长影响

罗汉果试管苗在不同波长的LED(半导体)蓝(475±5nm)、黄(585±5nm)、红(660±5nm)及普通日光灯下培养,25d后观测发现,其外观的优劣依次为:蓝光>白光>红光>黄光;植株重量:蓝光>红光>黄光>白光;蓝光和白光下的植株叶大、色绿,植株矮壮,侧芽多;红光和黄光下的植株叶小、色黄绿,植株高、细、弯曲、节间长。测定罗汉果成熟叶片的吸收光谱,发现在波长380~500nm及660~680nm处有较强吸收。不同的光质下测定成熟叶片光合速率,大小依次为:红光>蓝光>白光>黄光。上述的各项试验表明,蓝光对罗汉果幼苗生长发育最好;红光和蓝光为成熟叶片光合作用的最佳光源。     

Circular dichroism of helices formed by purine monomers with pyrimidine polynucleotides

The CD spectra of a number of helical complexes formed by purine monomers and complementary pyrimidine polyribonucleotides have been observed over the range 200–400 nm. Each of these spectra is quite similar to that of the corresponding polymer–polymer helix. The spectra are evidently determined by the geometry of the asymmetric array of bases, largely unperturbed by the ribose–phosphate backbone. The helix structure (A-form), on the other hand, is determined by the backbone of the pyrimidine homopolymer. Data on the monomer–polymer complexes support the conclusion that the CD spectra of ribohomopolymer helices depend primarily on interastrand interactions of the same transition within a given base and are relatively unaffected by transitions of the complementary base.     

Suppression of Recombination Losses in Polymer:Nonfullerene Acceptor Organic Solar Cells due to Aggregation Dependence of Acceptor Electron Affinity

Here, it is investigated whether an energetic cascade between mixed and pure regions assists in suppressing recombination losses in non‐fullerene acceptor (NFA)‐based organic solar cells. The impact of polymer‐NFA blend composition upon morphology, energetics, charge carrier recombination kinetics, and photocurrent properties are studied. By changing film composition, morphological structures are varied from consisting of highly intermixed polymer‐NFA phases to consisting of both intermixed and pure phase. Cyclic voltammetry is employed to investigate the impact of blend morphology upon NFA lowest unoccupied molecular orbital (LUMO) level energetics. Transient absorption spectroscopy reveals the importance of an energetic cascade between mixed and pure phases in the electron–hole dynamics in order to well separate spatially localized electron–hole pairs. Raman spectroscopy is used to investigate the origin of energetic shift of NFA LUMO levels. It appears that the increase in NFA electron affinity in pure phases relative to mixed phases is correlated with a transition from a relatively planar backbone structure of NFA in pure, aggregated phases, to a more twisted structure in molecularly mixed phases. The studies focus on addressing whether aggregation‐dependent acceptor LUMO level energetics are a general design requirement for both fullerene and NFAs, and quantifying the magnitude, origin, and impact of such energetic shifts upon device performance.     

X-ray analysis of the kinetics of Escherichia coli lipid and membrane structural transitions

Synchrotron radiation was used to follow the time course of the transitions, induced by temperature jump, in Escherichia coli membranes and their lipid extracts isolated from a fatty acid auxotroph grown with different fatty acids. We measured the relaxation times associated with the phase transitions as well as with the conformational transition of the hydrocarbon chains and observed different behavior as a function of chemical composition. Relaxation times of about 1-2 s were found at a hexagonal to lamellar phase transition and within a lamellar phase whose parameters display important variations with temperature when the conformational transition takes place. On the other hand, no delay was observed for a phase transition where large lipid or water diffusion was not needed. We have shown that phase transitions and conformational transitions are, to a large extent, uncoupled and that the relaxation times corresponding to the latter transition could be related to the size of the ordered domains. In all cases, the order to disorder conformational transition is more rapid than the disorder to order transition. Finally, the relaxation times of the disorder to order transition observed with the membranes and with their lipid extracts were found to be strongly correlated, indicating that the proteins do not play a role in this transition.     

Effect of light quality on somatic embryogenesis of quince leaves

The effect of light quality on somatic embryogenesis in quince BA 29 was investigated. 2,4-D induced leaves were exposed for 25 days to the following light quality treatments: dark, far-red, far-red+blue, far-red+red, blue, white, red+blue, red. After a further 20 days of white light exposure, somatic embryo production was recorded. Somatic embryogenesis was highest in cultures subjected to red light treatment, and decreased progressively with the transition to red+blue and to white. Overall, embryogenic competence showed a correlation with photoequilibrium. Phytochrome appeared to be inductive although this effect was adversely influenced by the blue absorbing photoreceptor, in particular at low photoequilibrium. Independently of light treatments applied, somatic embryos frequently showed severe morphological abnormalities. Conversion of somatic embryos to plantlets was not observed. This revised version was published online in June 2006 with corrections to the Cover Date.     

New characteristic signatures from time-dependent static light scattering during polymer depolymerization,with application to proteoglycan subunit degradation

Models were developed for the time-dependent light scattering intensity for simply branched (“comb”) polymers undergoing one or more of three distinguishable degradation mechanisms: (a) stripping off the side chains, (b) randomly degrading off the side chains, and (c) randomly degrading the backbone. The model equations were applied to the analysis of different types of degradation of simply branched biopolymers—bovine nasal cartilage proteoglycan subunits (or “monomers”); NaOH stripped off the glycosaminoglycan (GAG) chains from the protein backbone [mechanism (a)], whereas hyaluronidase seemed to randomly cleave the GAG side chains [mechanism (b)], and HCl both stripped the GAG side chains and randomly cleaved the protein backbone [combined mechanisms (a) and (c)]. The reactions were followed with time-dependent multiangle, static light scattering. The time-resolved total scattering technique allowed degradation rate constants and percentage of material in the branched polymer backbone and side chains to be determined, in addition to the mechanisms involved. These new time-dependent light scattering profiles are added to the growing library of functions from which deductions can be made concerning polymer structure and associated degradation mechanisms and kinetics. These conclusions, drawn from time-dependent “batch” light scattering, are substantiated by preliminary size exclusion chromatography results and chemical binding assays for sulfated GAGs. © 1995 John Wiley & Sons, Inc.     

Effects of light quality on the circadian rhythm of leaf movement of a short-day-plant

Studies were made of the effects of blue, green, red and far-red (FR) light on the circadian rhythm of leaf movement of Coleus blumei × C. frederici, a short day plant. Under continuous illumination with blue light, there was a significant lengthening of the period of the rhythm to about 24.0 hr, as compared to 22.5 hr in continuous darkness. Under continuous red light, the period length was significantly shortened to 20.5 hr. Under continuous green or FR, the period length was not significantly different from the dark control. It was observed that under continuous FR illumination, the leaves tended to oscillate in a more downward position. Eight-hr red light signals were effective in advancing the phase of the rhythm as compared to a control under continuous green light. Blue light signals were effective in delaying the phase of the rhythm. FR light signals were ineffective in producing either delay or advance phase shifts. Far-red light did not reverse the effects of either red or blue light signals. On the basis of these results it is suggested, that pigments which absorb blue or red light, rather than phytochrome, mediate the effect of light on the circadian rhythm of leaf movement.     

Effect of temperature on the induced cotton effects of acid polysaccharide-basic dye complexes

The induced Cotton effect of some acid polysaccharide–thiazine dye complexes were studied at various temperatures. When the equivalent ratio of the anionic site of the polymer to the cationic dye was near unity, all the complexes examined showed remarkable Cotton effects corresponding to their absorption bands in the visible and ultraviolet regions, at neutral pH and room temperature. Although the structure of the hyaluronate complex resembles the carbohydrate backbone, the sign of the Cotton effects was opposite that of chondroitin sulfate complexes. When the temperature was raised, the hyaluronate–toluidine blue complex decreased the metachromatic shift in the absorption spectrum gradually; the amplitude of the Cotton effects of this complex decreased also. With a polysaccharide which has a carboxylate group as its only anionic site (such as carboxymethylcellulose or pectic acid), a similar effect of temperature was observed on its induced Cotton effects. With the chondroitin 4-sulfate–toluidine blue complex, some reverse of the metachromatic shift was observed at higher temperature. However, the amplitude of its Cotton effects decreased up to 70 °C, then the sign of the effects reversed and the amplitude subsequently increased. A similar inversion of the sign of the Cotton effects was found with the chondroitin 6-sulfate–toluidine blue complex, but at a lower temperature (about 40 °C). Charonin sulfate, a highly sulfated cellulose-like glucan from a marine mollusca, showed a marked metachromatic effect on methylene blue even at the elevated temperature. The induced Cotton effects of this complex were also affected by temperature and the inversion of the sign was observed. When the pH was lowered, the amplitude of the Cotton effects of the hyaluronate-toluidine blue complex decreased and diminished at pH 3, at room temperature. With chondroitin 4-sulfate, the induced Cotton effects were remarkable at such a low pH; however, the amplitude of the effects decreased with elevated temperature and no inversion was observed. The optical rotatory dispersion of the chondroitin 6-sulfate–toluidine blue complex was reversed by acidifying to pH 3, and the amplitude of the Cotton effects decreased by elevating the temperature.     

Influence of chain length on exciton migration to low-energy sites in single fluorene copolymers.

Fluorescence spectroscopy was performed on single molecules of two 9,9-dialkylfluorene-benzothiadazole (FxBT) copolymers with a 10-fold difference in average molecular weight. Molecules of both polymers exhibit red-shifted emission indicative of energy migration to low-energy sites (LES) on the polymer chains; however, "red" spectra are much more common for the longer polymer. Since singlet-exciton migration is found to occur on the molecular length scale in both cases, the increased number of red-shifted spectra observed for the longer polymer is evidence that the likelihood of LES formation increases with chain length. This relationship is discussed in terms of three possible causes of low-energy sites: local polymer conformations, chromophores with extended conjugation lengths, and random chemical defects.     

Why inclusion bodies do assume different locations in thalassaemic erythrocytes

The reported scanning (SEM), transmission (TS), and freeze-etching (FE) electron microscopic studies have agreed in confirming that in thalassaemic erythrocytes, previously incubated with brilliant cresyl blue (BCB), the unpaired alpha chains precipitate in the central portions of the cell whereas excess beta chains locate in the submembranous regions. This is due to the fact that beta chains, possessing two thiols instead of only one (as in alpha chains), are more liable to bind to similar groups contained in the inner red cell leaflet. Less soluble alpha chains tend to form inter-chain bridges and thus precipitate centrally. SEM observations have given evidence that on the surface of the affected red cells denaturated alpha chains give rise to large and shallow invaginations whereas denatured beta chains lead to diffuse wrinkled appearance. The causes of the different SEM aspects have been suggested.     

Orientation and conformation of lipids in crystals of transmembrane proteins

Orientational order parameters and individual dihedral torsion angles are evaluated for phospholipid and glycolipid molecules that are resolved in X-ray structures of integral transmembrane proteins in crystals. The order parameters of the lipid chains and glycerol backbones in protein crystals are characterised by a much wider distribution of orientational order than is found in fluid lipid bilayers and reconstituted lipid–protein membranes. This indicates that the lipids that are resolved in crystals of membrane proteins are mostly not representative of the entire lipid–protein interface. Much of the chain configurational disorder of the membrane-bound lipids in crystals arises from C–C bonds in energetically disallowed skew conformations. This suggests configurational heterogeneity of the lipids at a single binding site: eclipsed conformations occur also in the glycerol backbone torsion angles and the C–C torsion angles of the lipid head groups. Conformations of the lipid glycerol backbone in protein crystals are not restricted to the gauche C1–C2 rotamers found invariably in phospholipid bilayer crystals. Lipid head-group conformations in the protein crystals also do not conform solely to the bent-down conformation, with gauche–gauche configuration of the phosphodiester, that is characteristic of phospholipid bilayer membranes. Stereochemical violations in the protein-bound lipids are evidenced by ester carboxyl groups in non-planar configurations, and even in the cis configuration. Some lipids have the incorrect enantiomeric configuration of the glycerol backbone, and many of the branched methyl groups in the phytanyl chains associated with bacteriorhodopsin have the incorrect S configuration.     

The evolution of male nuptial colour in a sexually dimorphic group of fishes (Percidae: Etheostomatinae)

To test hypotheses explaining variation in elaborate male colouration across closely related species groups, ancestral‐state reconstructions and tests of phylogenetic signal and correlated evolution were used to examine the evolution of male body and fin colouration in a group of sexually dichromatic stream fishes known as darters (Percidae: Etheostomatinae). The presence or absence of red–orange and blue–green male colour traits were scored across six body regions in 99 darter species using a recently estimated amplified fragment length polymorphism (AFLP) phylogeny for comparative analyses. Ancestral‐state reconstructions infer the most recent common ancestor of darters to lack red–orange colour and possess blue–green colour on different body regions, suggesting variation between species is due to independent gains of red–orange and losses of blue–green. Colour traits exhibit substantial phylogenetic signal and are highly correlated across body regions. Comparative analyses were repeated using an alternative phylogenetic hypothesis based on one mitochondrial and two nuclear genes, yielding similar results to analyses based on the AFLP phylogeny. Red–orange colouration in darters appears to be derived; whereas, blue–green appears to be ancestral, which suggests that different selection mechanisms may be acting on these two colour classes in darters.     

Synthesis, calorimetry, and X-ray diffraction of lecithins containing branched fatty acid chains

Lecithins with branched fatty acid chains were synthesized and characterized by differential scanning calorimetry and X-ray diffraction. The influence of three chemical alterations on the phase transition parameters were investigated: length of the branches in 2-position of the acyl chains, position of the branches in the acyl chains, and position of the branched fatty acid chains in the glycerol backbone. The results show that the branched phosphatidylcholines (PCs) have a reduced gel-to-liquid-crystalline phase transition temperature (Tm) compared to the corresponding straight-chain PCs. Depending on both the length of the branches in 2-position of the acyl chains and the position of the branches in the acyl chains, the Tm-values pass through a minimum. The systematic change of the main-transition temperatures Tm is connected with a modified structural polymorphism. If the length of the branches increases three types of polymorphism were observed.