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Cruise ports Alaska : a guide to perfect days on shore
Lonely Planet's Cruise Ports Alaska is your passport to the most relevant, up-to-date advice on what to see and skip, and what hidden discoveries await you. Watch the skyscrapers of downtown Vancouver disappear behind the trees of Stanley Park as you glide beneath the Lion's Gate Bridge, relive the wild drama of the gold rush era in Skagway, nose around Cold War relics amidst giant glaciers in Whittier; all with your trusted travel companion. Discover the best of Alaska and begin your journey now!
Book
How much do van der Waals dispersion forces contribute to molecular recognition in solution?
The emergent properties that arise from self-assembly and molecular recognition phenomena are a direct consequence of non-covalent interactions. Gas-phase measurements and computational methods point to the dominance of dispersion forces in molecular association, but solvent effects complicate the unambiguous quantification of these forces in solution. Here, we have used synthetic molecular balances to measure interactions between apolar alkyl chains in 31 organic, fluorous and aqueous solvent environments. The experimental interaction energies are an order of magnitude smaller than estimates of dispersion forces between alkyl chains that have been derived from vaporization enthalpies and dispersion-corrected calculations. Instead, it was found that cohesive solvent–solvent interactions are the major driving force behind apolar association in solution. The results suggest that theoretical models that implicate important roles for dispersion forces in molecular recognition events should be interpreted with caution in solvent-accessible systems.
Attractive van der Waals dispersion forces have been implicated in mechanisms as diverse as gecko adhesion and anaesthesia. Now, it has been found using synthetic molecular balances that dispersion forces between alkyl chains are an order of magnitude weaker in solution than they are in the gas phase.
Journal Article
Alaska
Describes points of interest and itineraries for each region of Alaska, and recommends the best outdoor activities, cultural events, restaurants, accomodations, and shopping centers.
Book
A genome assembly and the somatic genetic and epigenetic mutation rate in a wild long-lived perennial Populus trichocarpa
Background
Plants can transmit somatic mutations and epimutations to offspring, which in turn can affect fitness. Knowledge of the rate at which these variations arise is necessary to understand how plant development contributes to local adaption in an ecoevolutionary context, particularly in long-lived perennials.
Results
Here, we generate a new high-quality reference genome from the oldest branch of a wild
Populus trichocarpa
tree with two dominant stems which have been evolving independently for 330 years. By sampling multiple, age-estimated branches of this tree, we use a multi-omics approach to quantify age-related somatic changes at the genetic, epigenetic, and transcriptional level. We show that the per-year somatic mutation and epimutation rates are lower than in annuals and that transcriptional variation is mainly independent of age divergence and cytosine methylation. Furthermore, a detailed analysis of the somatic epimutation spectrum indicates that transgenerationally heritable epimutations originate mainly from DNA methylation maintenance errors during mitotic rather than during meiotic cell divisions.
Conclusion
Taken together, our study provides unprecedented insights into the origin of nucleotide and functional variation in a long-lived perennial plant.
Journal Article
Tuning singlet oxygen generation with caged organic photosensitizers
Controlling the succession of chemical processes with high specificity in complex systems is advantageous for widespread applications, from biomedical research to drug manufacturing. Despite synthetic advances in bioorthogonal and photochemical methodologies, there is a need for generic chemical approaches that can universally modulate photodynamic reactivity in organic photosensitizers. Herein we present a strategy to fine-tune the production of singlet oxygen in multiple photosensitive scaffolds under the activation of bioresponsive and bioorthogonal stimuli. We demonstrate that the photocatalytic activity of nitrobenzoselenadiazoles can be fully blocked by site-selective incorporation of electron-withdrawing carbamate moieties and restored on demand upon uncaging with a wide range of molecular triggers, including abiotic transition-metal catalysts. We also prove that this strategy can be expanded to most photosensitizers, including diverse structures and spectral properties. Finally, we show that such advanced control of singlet oxygen generation can be broadly applied to the photodynamic ablation of human cells as well as to regulate the release of singlet oxygen in the semi-synthesis of natural product drugs.
Generic chemical approaches that can universally modulate photodynamic reactivity in organic photosensitizers are of high interest. Here, the authors present a strategy to fine-tune the production of singlet oxygen in multiple photosensitive scaffolds under the activation of bioresponsive and bioorthogonal stimuli.
Journal Article
Ancient polymorphisms contribute to genome-wide variation by long-term balancing selection and divergent sorting in Boechera stricta
Background
Genomic variation is widespread, and both neutral and selective processes can generate similar patterns in the genome. These processes are not mutually exclusive, so it is difficult to infer the evolutionary mechanisms that govern population and species divergence.
Boechera stricta
is a perennial relative of
Arabidopsis thaliana
native to largely undisturbed habitats with two geographic and ecologically divergent subspecies. Here, we delineate the evolutionary processes driving the genetic diversity and population differentiation in this species.
Results
Using whole-genome re-sequencing data from 517
B. stricta
accessions, we identify four genetic groups that diverged around 30–180 thousand years ago, with long-term small effective population sizes and recent population expansion after the Last Glacial Maximum. We find three genomic regions with elevated nucleotide diversity, totaling about 10% of the genome. These three regions of elevated nucleotide diversity show excess of intermediate-frequency alleles, higher absolute divergence (
d
XY
), and lower relative divergence (
F
ST
) than genomic background, and significant enrichment in immune-related genes, reflecting long-term balancing selection. Scattered across the genome, we also find regions with both high
F
ST
and
d
XY
among the groups, termed
F
ST
-
islands. Population genetic signatures indicate that
F
ST
-
islands with elevated divergence, which have experienced directional selection, are derived from divergent sorting of ancient polymorphisms.
Conclusions
Our results suggest that long-term balancing selection on disease resistance genes may have maintained ancestral haplotypes across different geographical lineages, and unequal sorting of balanced polymorphisms may have generated genomic regions with elevated divergence. This study highlights the importance of ancestral balanced polymorphisms as crucial components of genome-wide variation.
Journal Article
Omics analyses and biochemical study of Phlebiopsis gigantea elucidate its degradation strategy of wood extractives
Wood extractives, solvent-soluble fractions of woody biomass, are considered to be a factor impeding or excluding fungal colonization on the freshly harvested conifers. Among wood decay fungi, the basidiomycete
Phlebiopsis gigantea
has evolved a unique enzyme system to efficiently transform or degrade conifer extractives but little is known about the mechanism(s). In this study, to clarify the mechanism(s) of softwood degradation, we examined the transcriptome, proteome, and metabolome of
P. gigantea
when grown on defined media containing microcrystalline cellulose and pine sapwood extractives. Beyond the conventional enzymes often associated with cellulose, hemicellulose and lignin degradation, an array of enzymes implicated in the metabolism of softwood lipophilic extractives such as fatty and resin acids, steroids and glycerides was significantly up-regulated. Among these, a highly expressed and inducible lipase is likely responsible for lipophilic extractive degradation, based on its extracellular location and our characterization of the recombinant enzyme. Our results provide insight into physiological roles of extractives in the interaction between wood and fungi.
Journal Article
Correction to: Ancient polymorphisms contribute to genome-wide variation by long-term balancing selection and divergent sorting in Boechera stricta
Following publication of the original article [1], the authors reported that the Availability of data and materials section required updating. The updated text reads as follows.Following publication of the original article [1], the authors reported that the Availability of data and materials section required updating. The updated text reads as follows.
Journal Article
Genome-wide role of codon usage on transcription and identification of potential regulators
Codon usage bias is a fundamental feature of all genomes and plays an important role in determining gene expression levels. The codon usage was thought to influence gene expression mainly due to its impact on translation. Recently, however, codon usage was shown to affect transcription of fungal and mammalian genes, indicating the existence of a gene regulatory phenomenon with unknown mechanism. In Neurospora, codon usage biases strongly correlate with mRNA levels genome-wide, and here we show that the correlation between codon usage and RNA levels is maintained in the nucleus. In addition, codon optimality is tightly correlated with both total and nuclear RNA levels, suggesting that codon usage broadly influences mRNA levels through transcription in a translation-independent manner. A large-scale RNA sequencing-based genetic screen in Neurospora identified 18 candidate factors that when deleted decreased the genome-wide correlation between codon usage and RNA levels and reduced the codon usage effect on gene expression. Most of these factors, such as the H3K36 methyltransferase, are chromatin regulators or transcription factors. Together, our results suggest that the transcriptional effect of codon usage is mediated by multiple transcriptional regulatory mechanisms.
Journal Article