Mechanical characteristics of artificial cell walls

Artificial plant cell walls were produced from bacterial cellulose and cell wall constituents. The artificial cell walls were stored at low, medium and high relative humidity, and then subjected to micro-mechanical tests. From chemical composition and microstructure analysis it was found that, among all artificial cell wall materials produced, the most representative analogue of natural apple cell wall was based on bacterial cellulose supplemented with xyloglucan and pectin. Uniaxial tensile tests revealed that the different cell wall materials differed in their mechanical properties; increasing the humidity during storage resulted in a decrease in the value of the secant modulus. The cell wall model material obtained may be used for the simulation of the effect of external factors on the physical and chemical properties of cell walls.     

Investigation of various factors for the extraction of peppermint (Mentha piperita L.) leaves

Ingredients from peppermint leaves are widely used in the food industry as food additives and natural flavours. The traditional way to produce mint extracts is via steam distillation or solvent extraction, both long and energy consuming processes. This paper investigated various extraction methods, namely room temperature extraction, reflux temperature extraction, ultrasonic assisted room temperature extraction and microwave-assisted extraction. Extraction of peppermint leaves was studied for extraction times of 5, 10, 30 and 60 min, varying the sample-to-solvent ratio, along with the study of extraction yields for three mint compounds, menthone, menthol and menthofuran. The use of microwave-assisted solvent extraction allows the reduction of process time, the reduction of solvent use, while increasing extraction yields.     

Tools and resources for Sz. pombe: a report from the 2006 European Fission Yeast Meeting

Schizosaccharomyces pombe has always suffered from a relative paucity of tools and resources, particularly when compared to Saccharomyces cerevisiae. The European Fission Yeast Meeting, held in March 2006, brought together a significant proportion of the Sz. pombe research community, so it was an ideal opportunity to hold a discussion session on the future needs of those working on this model organism. While the session generated a consensus on the most essential requirements, it also demonstrated the frustrations and concerns of those working with Sz. pombe. The community was also briefed regarding the future transition of the current database (Sz. pombe GeneDB) to a fully-fledged Model Organism Database (MOD) to support the needs of both fission yeast and the broader scientific community.     

Standardisation of methods for assessing mould germination: a workshop report

The first workshop on predictive mycology was held in Marseille, France, 2--4 February 2005 under the auspices of the French Microbiological society. The purpose of the workshop was to list the different techniques and definitions used by scientists for assessing mould germination and to evaluate the influence of the different techniques on the experimental results. Recommendations were made when a large consensus was obtained. In order to facilitate the study of germination, alternative methods to microscopic examination were examined.     

A Role for Human DNA Polymerase λ in Alternative Lengthening of Telomeres

Telomerase negative cancer cell types use the Alternative Lengthening of Telomeres (ALT) pathway to elongate telomeres ends. Here, we show that silencing human DNA polymerase (Pol λ) in ALT cells represses ALT activity and induces telomeric stress. In addition, replication stress in the absence of Pol λ, strongly affects the survival of ALT cells. In vitro, Pol λ can promote annealing of even a single G-rich telomeric repeat to its complementary strand and use it to prime DNA synthesis. The noncoding telomeric repeat containing RNA TERRA and replication protein A negatively regulate this activity, while the Protection of Telomeres protein 1 (POT1)/TPP1 heterodimer stimulates Pol λ. Pol λ associates with telomeres and colocalizes with TPP1 in cells. In summary, our data suggest a role of Pol λ in the maintenance of telomeres by the ALT mechanism.     

Alternative monomers for 4,4′-methylenedianiline in thermosetting epoxy resins

4,4′-Methylenedianiline (MDA) is utilized to produce high temperature epoxy resins as well as other high-performance composites; however, MDA is a known carcinogen and liver toxicant. Novel dianilines derived from both petroleum and biomass with different quantities and types of methyl and methoxy substituents on the aromatic ring were prepared and studied to reduce toxicity and carcinogenic aspects of the resulting material while maintaining thermal and mechanical integrity. These dianilines were primarily prepared by coupling commercial anilines using paraformaldehyde under acidic conditions. Another dianiline was prepared by nitration of bisphenol A and subsequent reduction of the nitrates to amines. Structure–toxicity relationships indicate that multiple substituents on the aromatic ring are necessary to reduce the toxicity of the dianiline. Epoxy-amine resins were prepared by blending the dianilines with 50 wt % Epikure W liquid amine curing agent and mixing with a stoichiometric amount of EPON 828 epoxy resin. Methoxy and methyl substituents increase the melting point of the dianilines by as much as 65 °C, thereby worsening the processing of these monomers as liquid thermoset resins. Structure–property relationships show that the addition of a methoxy group to the aromatic ring and moving the amine from the 4,4′ position on the dianiline reduces the glass transition temperature (T _g) by approximately 10 °C. A single methyl group has little effect on T _g and two methyl groups increase the T _g only when both are ortho to the amine, yet this causes a large 14 °C increase in T _g. Thermal degradation profiles are not significantly affected by the dianiline. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48707.     

Chemical Deterrence of a Cyanobacterial Metabolite against Generalized and Specialized Grazers

Pitipeptolide A is the major secondary metabolite in a persistent population of the cyanobacterium Lyngbya majuscula from Guam. Because this cyanobacterium is of low preference to many sympatric consumers, we tested the hypothesis that this compound acted as a chemical defense. Pitipeptolide A was deterrent to urchins, two species of amphipods, and small herbivorous crabs, whereas it did not deter feeding by the sea hare Stylocheilus striatus, which readily consumes cyanobacteria. Although our comparison included various small invertebrates, which are often tolerant to algal chemical defenses, this cyanobacterial compound proved deterrent at natural concentrations to all but one of the consumer species tested. Thus, the production of defensive secondary metabolites is likely related to the common occurrence of L. majuscula on this coral reef despite the abundance of diverse grazers.     

Development of selective estrogen receptor modulator (SERM)-like activity through an indirect mechanism of estrogen receptor antagonism: defining the binding mode of 7-oxabicyclo[2.2.1]hept-5-ene scaffold core ligands

Previously, we discovered estrogen receptor (ER) ligands with a novel three-dimensional oxabicyclo[2.2.1]heptene core scaffold and good ER binding affinity act as partial agonists via small alkyl ester substitutions on the bicyclic core that indirectly modulate the critical switch helix in the ER ligand binding domain, helix 12, by interactions with helix 11. This contrasts with the mechanism of action of tamoxifen, which directly pushes helix 12 out of the conformation required for gene activation. We now report that a much larger substitution can be tolerated at this position of the bicyclic core scaffold, namely a phenyl sulfonate group, which defines a novel binding epitope for the estrogen receptor. We prepared an array of 14 oxabicycloheptene sulfonates, varying the phenyl sulfonate group. As with the parent compound, 5,6-bis-(4-hydroxyphenyl)-7-oxabicyclo[2.2.1]hept-5-ene-2-sulfonic acid phenyl ester (OBHS), these compounds showed preferential affinity for ERα, and the disposition and size of the phenyl substituents were important determinants of the binding affinity and selectivity of these compounds, with those having ortho substituents giving the highest, and para substituents the lowest affinities for ERα. A few analogues exhibit ERα binding affinities that are comparable to or, in the case of the ortho-chloro analogue, higher than that of OBHS itself. In cell-based studies, we found several compounds with activity profiles comparable to tamoxifen, but acting entirely as indirect antagonists, allosterically interfering with recruitment of coactivator proteins to the receptor. Thus, the OBHS binding epitope represents a novel approach to the development of estrogen receptor antagonists via an indirect mechanism of antagonism.