Cis-trans Research Articles

Uncovering the conditions that dictate the liquid-liquid phase separation of the CTD of RNAPII.

The intrinsically disordered carboxy terminal domain (CTD) of RNA polymerase II (RNAPII) may nucleate the formation of transcription factories through a mechanism of liquid-liquid phase separation (LLPS). Transcription factories are densely packed membraneless organelles (MLOs) that contain all the necessary components to perform the transcription cycle. The CTD in model organisms such as S. cerevisiae, S. pombe and C. albicans, is composed of ∼26 copies of consensus repeats (Y1S2P3T4S5P6S7). However, CTD sequences of fungi isolated from geographically distinct locations from temperate to polar regions, show high sequence diversity at positions 1, 4, and 7. The CTD is highly conserved at its Ser-Pro motifs, which are targets of phosphorylation and cis-trans prolyl isomerization by Ess1. Ess1, an essential peptidylprolyl isomerase in yeast, has a highly conserved evolutionary relationship with the CTD. Here, we found that different CTDs isolated from yeasts found in geographically distinct regions ranging from temperate to polar climates undergo LLPS, but do so differently. We hypothesize Ess1 and phosphorylation may modulate the phase behavior of the CTD. The objective of this study is to determine how linear amino acid sequence, phosphorylation, and cis-trans prolyl isomerization influences CTD phase behavior. To do so, we utilize a variety of biophysical characterization assays such as UV-Vis spectroscopy, DIC microscopy, and phase separation prediction algorithms. These results will elucidate what conditions promote the LLPS of the CTD and its orthologs, thereby setting the stage for further investigating the conditions that promote the formation of transcription factories.

Photo-control of small GTPase Ras GTPase cycle using photochromic molecule.

The small G protein Ras is a central regulator of cellular signal transduction processes, functioning as a molecular switch. Structure and regulatory mechanisms of Ras have been well studied at the molecular level. In this study, we have tried to photocontrol of Ras function using photochromic molecule as a regulatory molecular device. The two methods utilizing azobenzene derivatives as photochromic molecule were employed. The first one is that incorporating bifunctional azobenzene derivatives into the inhibitory peptides and photocontrol Ras function with the photoswitching inhibitory peptide. The second one is to incorporate azobenzene derivatives directly into the functional site of GEF. Recently, a novel peptide inhibitor of Ras (KRpep-2d) was reported to inhibit the guanine nucleotide exchange of Ras with GEF potently. We prepared the KRpep-2d modified with azobenzene derivative (ABDM, DIAAB, BSBCA22) to photocontrol of Ras GTPase activity. The GAP and GEF dependent GTPase of Ras was measured in the presence of peptide inhibitor upon UV and visible light irradiations. We also examined the photocontrol of Ras GTPase by incorporation of azobenzene into the functional site of GEF. The GEF mutant S732C, S881C, H905C, H911C and K679C were prepared and modified with phenylazophenyl maleimide (PAM), Amino azobenzene maleimide (AABM), Sulfonate azobenzene maleimide (SABM). These mutants modified with PAM did not show significant change of GTPase activity accompanied by cis-trans isomerization. Activity of these mutants decrease lower than wild type, but mutant(K679C) does not decrease.

Effect of Processing Method on Carotenoid Profiles of Oils from Three Varieties of Nigerian Palm Oil (Elaise guinensis)

Purpose: This study assessed the effect of processing method on the carotenoid profile of oil from three varieties of the Nigerian oil palm fruits (elaise guinensis). Specific varieties of the elaise guinensis, which are the dura, pesifera and tenera were obtained from National Institute for oil palm research (NIFOR) in Edo state.
 Methodology: The samples were divided into two and processed in two different methods as commonly practiced in the East, the hot and cold processes. The oil extracted from each of the process was then analyzed for oil characteristics using standard analytical methods while the carotenoid profile was analyze using HPLC C21 column. The results generated were subjected to one-way analysis of variance (ANOVA).
 Findings: The results of carotenoid constituent indentified include: lutein, neurosporene (trans), neurosporene (cis), α-Zeacarotene(cis), α-Zeacarotene(trans), phytoene, phytofluene, β-zeacarotene, 13 and 13’ cis α-carotene, 13 cis β-carotene, trans α-carotene, 9 cis α-carotene, trans β-carotene, αcarotene a(cis), α-carotene b(cis), α-carotene (trans), γ-carotene (trans), γ-carotene b(cis), lycopene (cis) and lycopene (trans). The results of physicochemical characteristics of the oil samples extracted range from 0.9220.004 - 0.9160.001 for specific gravity (SG), 8.100.17 - 4.880.04 mg KOH/g for acid value, 4.290.02 - 2.440.02 % for free fatty acid value (FFA), 6.000.21 to 204.670.98 mgKOH/g for saponification value and 9.530.23 - 5.250.33 mEq/kg; for peroxide value while the carotenoids values were between 53.735±0.10 and 123.389± 0.20 mg/100g.
 Unique Contribution to Theory, Practice and Policy: From the result we can observe that the main constituent of the palm oil carotenoid is the β -carotene which makes up to about 80% of the total carotene. Statistical analysis revealed that no significant difference exists between the mean of each of the processing method on the carotenoid profile of the oil sample analyzed.

Femtosecond dynamics of rhodopsin revealed by X-ray laser.

G-protein-coupled receptors of the Rhodopsin family are implicated in transmitting signals across biomembranes and are among the most widespread pharmaceutical targets. For G-protein-coupled receptors (GPCRs) like rhodopsin, an important question is how the rapid local dynamics of the ligand initiate the functional protein transitions. Despite the availability of crystal structures of rhodopsin and cryo-trapped intermediates, it is unclear how the protein dynamics are affected by lattice-packing forces or low temperatures. We hypothesize that the crystalline environment inhibits the full range of conformational motions in the visual activation. Here we show how solution X-ray scattering combined with molecular simulations informs the functional dynamics of membrane proteins. To follow the protein structural changes due to light absorption by retinal, we conducted time-resolved X-ray solution scattering (TR-XSS) studies of detergent-solubilized rhodopsin. Femtosecond solution X-ray scattering using an X-ray free electron laser (XFEL) detected the protein structural change in the absence of a crystal lattice and allowed the first direct observation of cis-trans isomerization of retinal bound to visual rhodopsin as it occurred in real time [1]. We discovered a significant difference-scattering signal within the first few time points immediately following the pump laser triggering event. Two scattering components were found within 10 ps after photoactivation at ambient temperature. The first was consistent with structurally similar photo/bathorhodopsin intermediates, and the second due to changes in solvent dynamics. Interpretation of the TR-XSS profiles using molecular dynamics simulations reveal significant atomic displacements in the β-ionone ring, and the amino acids like Tyr268 previously thought to occur later in the photocycle. Our findings demonstrate how X-ray scattering with an XFEL informs the functional dynamics of GPCRs, without artifacts caused by crystal packing or cryo-trapping photointermediates. [1] M.F. Brown et al. (2022) Biophys. J. 121, 193a.

Multi-stimuli responsive property and photopatterning of an acylhydrazone derivative

A new dimethylamino-substituted anthracylhydrazone derivative AHY was synthesized and its multi-stimuli responsive property and photopatterning behavior were studied. AHY showed mechanofluorochromic behavior, accompanied by emission color from green to yellow upon grinding. Secondly, significant acidochromism was observed for AHY film, i.e. from yellow to orange under natural light. In addition, the original green fluorescence could be quenched upon treatment by TFA. Furthermore, the photoluminescence quenching phenomenon and photopatterning of AHY film were attributed to the trans-cis isomerization of –CN- upon photo-irradiation.

Understanding the Cis-Trans Amide Bond Isomerization of N,N'-Diacylhydrazines to Develop Guidelines for A Priori Prediction of Their Most Stable Solution Conformers.

N,N'-diacylhydrazines (R1CO-NR3-NR4-COR2) are a class of small molecules with a wide range of applications in chemistry and biology. They are structurally unique in the sense that their two amide groups are connected via a N-N single bond, and as a result, these molecules can exist in eight different isomeric forms. Four of these are amide isomers [trans-trans (t-t), trans-cis (t-c), cis-trans (c-t), and cis-cis (c-c)] arising from C-N bond restricted rotation. In addition, each of these amide isomers can exist in two different isomeric forms due to N-N bond restricted rotation, especially when R3 and R4 groups are relatively bigger. Herein, we have systematically investigated the conformations of 55 N,N'-diacylhydrazines using a combination of solution NMR spectroscopy, X-ray crystallography, and density functional theory calculations. Our data suggest that when the substituents R3 and R4 on the nitrogen atoms are both hydrogens. These molecules prefer twisted trans-trans (t-t) (>90%) geometries (H-N-C═O ∼ 180°), whereas the N-alkylated and N,N'-dialkylated molecules prefer twisted trans-cis (t-c) geometries. Herein, we have analyzed the stabilization of the various isomers of these molecules in light of steric and stereoelectronic effects. We provide a guideline to a priori predict the most stable conformers of the N,N'-diacylhydrazines just by examining their substituents (R1-R4).

Thermal Half-Lives of Azobenzene Derivatives: Virtual Screening Based on Intersystem Crossing Using a Machine Learning Potential.

Molecular photoswitches are the foundation of light-activated drugs. A key photoswitch is azobenzene, which exhibits trans-cis isomerism in response to light. The thermal half-life of the cis isomer is of crucial importance, since it controls the duration of the light-induced biological effect. Here we introduce a computational tool for predicting the thermal half-lives of azobenzene derivatives. Our automated approach uses a fast and accurate machine learning potential trained on quantum chemistry data. Building on well-established earlier evidence, we argue that thermal isomerization proceeds through rotation mediated by intersystem crossing, and incorporate this mechanism into our automated workflow. We use our approach to predict the thermal half-lives of 19,000 azobenzene derivatives. We explore trends and trade-offs between barriers and absorption wavelengths, and open-source our data and software to accelerate research in photopharmacology.

Trans-cis isomerization kinetics of cyanine dyes reports on the folding states of exogeneous RNA G-quadruplexes in live cells.

Guanine (G)-rich nucleic acids are prone to assemble into four-stranded structures, so-called G-quadruplexes. Abnormal GGGGCC repeat elongations, and in particular their folding states, are associated with amyotrophic lateral sclerosis and frontotemporal dementia. Due to methodological constraints however, most studies of G quadruplex structures are restricted to in vitro conditions. Evidence of how GGGGCC repeats form into G-quadruplexes in vivo is sparse. We devised a readout strategy, exploiting the sensitivity of trans-cis isomerization of cyanine dyes to local viscosity and sterical constraints. Thereby, folding states of cyanine-labeled RNA, and in particular G-quadruplexes, can be identified in a sensitive manner. The isomerization kinetics, monitored via fluorescence blinking generated upon transitions between a fluorescent trans isomer and a non-fluorescent cis isomer, was first characterized for RNA with GGGGCC repeats in aqueous solution using fluorescence correlation spectroscopy and transient state (TRAST) monitoring. With TRAST, monitoring the isomerization kinetics from how the average fluorescence intensity varies with laser excitation modulation characteristics, we could then detect folding states of fluorescently tagged RNA introduced into live cells.

Moroccan Endemic Artemisia herba-alba Essential Oil: GC-MS Analysis and Antibacterial and Antifungal Investigation

In Morocco, the endemic Artemisia herba-alba is well known by its traditional uses and health benefits. The search for natural, safe, and effective antibacterial and antifungal agents from plants is in high demand due to microbial and fungal resistance to conventional synthetic antibiotics and antifungal drugs. In this study, the A. herba-alba was collected from the region of Fez-Boulemane during the periods of March, June, and September. Essential oils (EOs) were extracted from the aerial part of the plant by the hydrodistillation method. The chemical constituents were determined using GC-MS as analytical tools. The antimicrobial activities of different oils were tested using the macrodilution method. The results showed the difference in the yields between the three EOs (0.49, 1.74, 1.30% (mL/100 g)), respectively, as well as in their corresponding chemical compositions. The main constituents revealed by GC-MS are higher contents of oxygenated monoterpenes (84.7, 84.4, 81%), such as cis chrysanthenyl acetate (30, 26.7, 27.6%), β-thujone (23.2, 12.9, 15.4%), camphor (9.76, 14.3, 15.8%), chrysanthenone (2.4, 1, 14%), 1,8-cineole (1.5, 11.7, 11.8%), trans β-dihydroterpineol (7.8, 7.2, 6.9%), α-thujone (4.8, 3, 5.4%), and sesquiterpenic davanone (3.9, 1.5, 1.4%), respectively. The three EOs biological activities’ results showed significant antimicrobial effects against four bacteria tested (E. coli, B. subtilis, S. aureus, M. luteus), with the MIC values ranging from 0.1 to 0.03% (v/v), as well as interesting antifungal effects on both wood rot fungi against four fungi examined (G. trabeum, P. placenta, C. puteana, C. versicolor) and molds against three microorganisms tested (A. niger, P. digitatum, P. expansum), with MIC values ranging from 0.2 to 0.03% (v/v) and 0.4 to 0.03% (v/v), respectively. The June and September EO samples showed more potent activities than those collected during March. Our research findings showed quantitative variability in both EO contents and chemical compositions, which could be due to the phenological stages, climatic conditions of growth, and harvesting periods. The potent results of the antimicrobial/antifungal activities were provided by the EOs of June and September and might be correlated to the contribution and synergism effect of all oxygenated monoterpenes. These results support the possible application of A. herba-alba EOs as natural and safe antibacterial agents, and an effective alternative to synthetic drugs, enabling the prevention and treatment of certain pathogenic infections in food and health, and the preservation of wood alteration against fungi.

Isomerization-Controlled Proton-Electron Coupling in a π-Planar Metal Complex.

Proton-coupled electron transfer (PCET) is a ubiquitous and fundamental process in biochemistry and electrochemistry performed by transition-metal complexes. Most synthetic efforts have been devoted to selecting the components, that is, metal ions and ligands, to control the proton-electron coupling. Here, we show the first example of controlling the proton-electron coupling using the cis-trans metal-ligand isomerization in a π-planar platinum complex, Pt(itsq)2 (itsq1-: o-iminothiosemiquinonate). Both the isomers, which were obtained separately, were characterized by single-crystal X-ray diffraction, and the cis-to-trans isomerization was achieved by immersing in organic solvents. Theoretical calculations predicted that the proton-electron coupling evaluated from the energetic stabilization of the lowest unoccupied molecular orbital by protonation varies greatly depending on the geometrical configuration compared to the metal substitution.

A study of azopyrimidine photoswitches and their interactions with cyclodextrins: When the guest governs the type of accommodation at the host

Azopyrimidines have recently emerged as a new class of photoswitches structurally similar to azobenzenes switching between trans and cis isomers. These compounds have a wide range of potential applications in photopharmacology, catalysis or as molecular devices, but their low solubility in water limits their biological applications. Nevertheless, this drawback could be overcome by their inclusion into supramolecular structures. To test this hypothesis, we prepared a series of azopyrimidines and investigated their structure, cis-trans isomerization and host-guest chemistry with cyclodextrins (CDs) using an experimental-theoretical approach combining capillary electrophoresis (CE), Nuclear Magnetic Resonance (NMR) spectroscopy and computational models. The results revealed that β-CD exhibits high selectivity over several CDs tested for the accommodation of the studied compounds. Orientation of guests in inclusion complexes was experimentally assessed by Nuclear Overhauser Effect (NOE) contacts and supported by quantum-chemical calculations. Moreover, investigation of noncovalent interactions of azopyrimidines with β-CD by CE showed that azopyrimidines with suitable structural modification can form strong complexes with high values of binding constants (over 17 000 L mol−1). For such complexes, trans-cis isomerization proceeds directly inside the β-CD cavity with azopyrimidine remaining encapsulated through its narrower primary portal. By contrast, in weakly interacting complexes, the trans isomer is released, and the cis isomer is generated outside the cavity. In subsequent re-complexation, the cis isomer is then re-captured through the wider secondary portal. Therefore, our findings point to two significantly different complexation processes depending on substitutional pattern and binding constant values of azopyrimidines; a feature which may lead to future promising applications.

Solvent-Controlled Photoswitching of Azobenzene: An Excited State Shuttle.

Light controlled excited state trans-cis isomerization process is a key to the development of conversion of light energy to mechanical motion at the molecular level. Considerable efforts have been made in tuning the isomerization process with electron donor and acceptor substituents by altering the excited state reaction coordinate. Here, we report a two novel push-pull series of para-diethylamino (DEA) and diphenylamino (DPA) substituted (E)-4'-((4-(diethylamino)phenyl)diazenyl)-N,N-diphenyl-[1,1'-biphenyl]-4-amine (1) and (E)-4'-((4-(diphenylamino)phenyl)diazenyl)-N,N-diphenyl-[1,1'-biphenyl]-4-amine (2). Compound 1 and 2 undergoes both photochemical and photophysical excited state deactivation pathways which can be controlled by varying the solvent polarity. These structural motifs of 1 and 2 would undergo torsional motions upon excitation to exhibit either trans → cis photoisomerization or to form a twisted intramolecular charge transfer state and both the process originates from the same excited state and competes with each other. Thus, alternations in the surrounding environment such as solvent polarity, solution viscosity, and protonation were employed to understand the preferential excited state deactivation pathway and thereby these systems could be employed as a new class of azobenzene-based luminescent photochromic molecules. For instance, in nonpolar solvent, toluene photoisomerization is preferred over TICT, but polar solvent, ethanol preferentially stabilizes the TICT state by virtue of N-C rotation which renders the energy barrier unfavourable for photoisomerization. The photostationary state of 1 in toluene is predominantly the Z isomer, whereas in ethanol E isomer is nearly two-fold higher than the Z isomer. These feature sets up a new approach towards the construction of multinary molecular switches and subsequent development in diverse fields.

Combining Electro-, Photo-, and Biocatalysis for One-Pot Selective Conversion of Furfural into Value-Added C4 Chemicals

Chemobiocatalysis has emerged as a powerful tool in synthetic chemistry, but one-pot multistep syntheses incorporating multiple types of catalysts remain challenging because of the greatly increased incompatible issues between different catalysts. In this work, we reported the combination of electro-, photo-, and biocatalysis for one-pot selective valorization of biomass-derived furfural into various C4 chemicals including maleic acid (MA), fumaric acid (FA), d- and l-malic acid (MalA), and l-aspartic acid (l-Asp). MA was concurrently synthesized from furfural via a cascade of electrochemical oxidations with 4-acetamido-2,2,6,6-tetramethylpiperidine-N-oxyl (ACT) and photo-oxygenation with eosin Y (EY) with up to a 97% yield. ACT is a versatile catalyst capable of oxidizing both furfural and intermediate 5-hydroxy-2-(5H)-furanone. Then, biocatalysis was harnessed to produce enantiopure chemicals after photoelectrocatalysis. Furfural was selectively converted to d-MalA via sequential photoelectrooxidation and biocatalytic hydration with a 91% yield as maleate hydratase was readily inactivated under light irradiation. Also, maleate cis–trans isomerase (MaiA) was found to be highly sensitive to chemical oxidation; thus, two-step synthesis of FA and its derivatives l-MalA and l-Asp was performed by sequentially using ACT/EY and one/dual-enzyme with 79–97% yields. Both catalyst and reaction engineering strategies were applied to address the incompatibility between MaiA and photoelectrooxidation. Consequently, FA was produced from furfural in a concurrent manner with a 67% yield. The present work demonstrates the great power of chemobiocatalysis in the valorization of platform chemicals.

Elucidating effect of acid strength on isomerization mechanisms of butene over solid acid catalysts in C4 alkylation

Understanding the effect of acid strength on butene isomerization mechanisms is essential in C4 alkylation process. Herein, the double bond, trans-cis, and skeleton isomerization mechanisms of butene over acid sites with different acid strengths were investigated utilizing density functional theory (DFT) calculations. It is demonstrated that the acid strength significantly affects the isomerization mechanisms of butene. The stability of carbonium ions as reaction intermediates follows the order: tert-butyl cation > cis-butyl cation > trans-butyl cation, which is more sensitive to acid strength than that of butoxide species. Therefore, the reaction pathways of double bond and trans-cis isomerizations changed with varying the acid strength. Based on the analysis of activation energy barriers, it is found that 1-butene and 2-butene can be easily converted into each other over strong acid site. Thus, for reactants, C4 alkylation has no selectivity to 1-butene and 2-butene over strong acid site, which is consistent with experimental study. This work provides mechanistic insights into the relationship among acid strength, type of butene, and quality of alkylate in the C4 alkylation process.

Polyacrylate Backbone Promotes Photoinduced Reversible Solid-To-Liquid Transitions of Azobenzene-Containing Polymers

The development of polymers with efficient photoinduced reversible solid-to-liquid transitions is desirable for the design of healable materials, reconfigurable devices, and switchable adhesives. Herein, we demonstrate that an azobenzene-containing polyacrylate P-H exhibits more efficient photoinduced reversible solid-to-liquid transitions than its polymethacrylate analogue P-Me. The side chain of P-H or P-Me contains a hexamethylene spacer, a photoresponsive azobenzene group, and an n-decyl tail. Both P-H and P-Me show reversible cis–trans photoisomerization. Solid transP-H and P-Me change to liquid cis ones via UV-light-induced trans-to-cis isomerization; liquid cisP-H and P-Me revert to solid trans ones via visible-light-induced cis-to-trans back isomerization. Differential scanning calorimetry and rheology measurements revealed that photoinduced reversible solid-to-liquid transitions occur because P-H and P-Me have photoswitchable glass transition temperatures. Although P-Me exhibits a slightly faster rate for trans-to-cis photoisomerization than P-H due to fewer aggregates in solid state, cisP-H flows 20 times faster than cisP-Me because P-H has a more flexible polymer backbone. The low viscosity of cisP-H makes photoinduced solid-to-liquid transition efficient and enables the design of rapidly healable coatings. Our study shows that the design of a flexible backbone is a new strategy to develop rapidly healable polymers with more efficient photoinduced solid-to-liquid transitions.

Regulation of eukaryotic protein kinases by Pin1, a peptidyl-prolyl isomerase.

The peptidyl-prolyl isomerase Pin1 cooperates with proline-directed kinases and phosphatases to regulate multiple oncogenic pathways. Pin1 specifically recognizes phosphorylated Ser/Thr-Pro motifs in proteins and catalyzes their cis-trans isomerization. The Pin1-catalyzed conformational changes determine the stability, activity, and subcellular localization of numerous protein substrates. We conducted a survey of eukaryotic protein kinases that are regulated by Pin1 and whose Pin1 binding sites have been identified. Our analyses reveal that Pin1 target sites in kinases do not fall exclusively within the intrinsically disordered regions of these enzymes. Rather, they fall into three groups based on their location: (i) within the catalytic kinase domain, (ii) in the C-terminal kinase region, and (iii) in regulatory domains. Some of the kinases downregulated by Pin1 activity are tumor-suppressing, and all kinases upregulated by Pin1 activity are functionally pro-oncogenic. These findings further reinforce the rationale for developing Pin1-specific inhibitors as attractive pharmaceuticals for cancer therapy.

Trans Women, Cis Women, Alien Women, and Robot Women Are Women: They Are All (Simply) Adults Gendered Female

AbstractAlex Byrne contends that women are (simply) adult human females, claiming that this thesis has considerably greater initial appeal than the justified true belief (JTB) theory of knowledge. This article refutes Byrne's thesis in the same way the JTB theory of knowledge is widely thought to have been refuted: through simple counterexamples. Lessons are drawn. One lesson is that women need not be human. A second lesson is that biology and physical phenotypes are both irrelevant to whether someone is a woman, and indeed, female in a gendered sense. A third lesson is that trans women, cis women, alien women, and robot women are all women because to be a woman is to be an adult gendered female. This article does not purport to settle complex normative questions of ethics or justice, including whether the ordinary meaning of woman ought to be retained or changed—though I do note plausible implications for these debates. This article does purport to settle what the ordinary meaning of woman is, and in that regard contribute to important conceptual ground-clearing regarding what constitutes an ameliorative or revisionary definition of woman.

Qualitative and quantitative phytochemical analysis of methanolic extract of Magnolia champaca leaves

Plants remain a vibrant source of diverse bioactive phytochemicals that are secondary metabolites protecting them from infections and predations. Magnolia champaca is reported to possess a multitude of phytochemicals. In the present study, the phytochemical constituents of the methanolic extract of Magnolia champaca leaves were analysed qualitatively and with gas chromatography-tandem mass spectrometry (GC-MS/MS). Fourier transform infrared (FTIR) spectroscopic analysis was performed to identify the chemical nature of the extract and to find structurally similar compounds. Preliminary phytochemical screening revealed the presence of alkaloids, flavonoids, terpenes, glycosides, phenols, steroids, tannins and saponins. FTIR spectroscopic analysis revealed structurally related compounds. GC-MS/MS analysis revealed the presence of 99 diverse compounds with varied biological activities, among which 1,2,4-butanetriol, n-hexadecanoic acid, cis vaccenic acid, phytol, trans longipinocarveol and caryophyllene oxide were found predominantly. Thus, the identification and characterisation of the phytochemicals in the extract favour the development of novel therapeutic agents.

Optical and computational study of the trans ↔ cis reversible isomerization of the commercial bis-azo dye Bismarck Brown Y.

The trans-cis-trans isomerization behaviour of Bismarck Brown Y (BBY) during and after irradiation with visible light, was characterized in detail for the first time by means of optical pump-probe experiments, to study the geometric inter-conversion of bis-azobenzene both in solution and embedded in multi-layered polymeric thin films. The rate constants observed for the thermal cis-trans back isomerization permit a determination of how the thermal isomerization is influenced by its local environment. In both solution and when incorporated into multi-layered thin films, the thermal relaxation observed for the commercial azo dye BBY showed a highly unusual biexponential decay, which clearly demonstrates two distinct isomerization processes. The cis decay showed an anomalous fast isomerization process on the timescale of milliseconds, followed by a slower isomerization process with a cis lifetime on the order of seconds. It was further observed that the faster isomerization process was influenced more by its local environment than was the slower process. The faster isomerization process also displayed a higher rate constant in aprotic solvents such as THF and DMF compared to that observed in protic solvents such as ethanol and water. Additionally, a higher rate constant was observed in solution compared to the multi-layered thin films where motion of the azo molecules was likely more restricted. Following recrystallization of the BBY azo dye, the more expected monoexponential decay was observed for the cis isomer in solution, with a single cis lifetime calculated on the timescale of seconds. This timescale corresponded well to values predicted by density functional theory calculations.

Conformational preferences of aza-proline residues and their impact on the relative stability of polyproline structures

The collagen model peptide Ac-(Hyp-Gly-Pro)2-NMe2 with the replacement of Pro3 by azPro in the middle of the sequence well adopted polyproline II structures with RMSD = 0.6 Å in water.