Radiolabel Uncovers Nonintuitive Metabolites of BIIB104: Novel Release of [14C]Cyanide from 2-Cyanothiophene and Subsequent Formation of [14C]Thiocyanate.

BIIB104 (formerly PF-04958242), N-((3S,4S)-4-(4-(5-cyanothiophen-2-yl)phenoxy)tetrahydrofuran-3-yl)propane-2-sulfonamide, is an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor potentiator investigated for the treatment of cognitive impairment associated with schizophrenia. Preliminary in vitro metabolism studies with non-radiolabeled BIIB104 in rat, dog, and human liver microsomes (RLM, DLM, and HLM) showed O-dealkylation in all three species, tetrahydrofuran hydroxylation dominating in DLM and HLM, and thiophene hydroxylation prevalent in RLM. However, a subsequent rat mass balance study with [nitrile-14C]BIIB104 showed incomplete recovery of administered radioactivity (∼80%) from urine and feces over 7 days following an oral dose, and an exceptionally long plasma total radioactivity half-life. Radiochromatographic metabolite profiling and identification, including chemical derivation, revealed that [14C]cyanide was a major metabolite of [nitrile-14C]BIIB104 in RLM, but a minor and trace metabolite in DLM and HLM, respectively. Correspondingly in bile duct-cannulated rats, [14C]thiocyanate accounted for ∼53% of total radioactivity excreted over 48 hours postdose and it, as an endogenous substance, explained the exceptionally long plasma radioactivity half-life. The release of [14C]cyanide from the 2-cyanothiophene moiety is postulated to follow an epoxidation-initiated thiophene-opening based on the detection of non-radiolabeled counterpart metabolites in RLM. This unusual biotransformation serves as a lesson regarding placement of the radioactive label on an aryl nitrile when material will be used for evaluating the metabolism of a new drug candidate. Additionally, the potential cyanide metabolite of nitrile-containing drug molecules may be detected in liver microsomes with liquid chromatography-mass spectrometry following a chemical derivatization. SIGNIFICANCE STATEMENT: Using [nitrile-14C]BIIB104, non-intuitive metabolites of BIIB104 were discovered involving a novel cyanide release from the 2-cyanothiophene motif via a postulated epoxidation-initiated thiophene-opening. This unusual biotransformation serves as a lesson regarding placement of the radioactive label on an aryl nitrile when material will be used for evaluating the metabolism of a new drug candidate.

Working and impacting local communities as establishing the start of a conservation initiative: American Society of Primatology conservation committee webinar.

Nonhuman primate species currently face human-induced pressures and will continue to face them in the modern landscape. These pressures require conservation projects in primate habitat countries to aid in protection, preservation, and conservation. Though there are several examples of primate conservation projects, starting up an initiative can be a daunting task. The American Society of Primatology (ASP) Conservation Committee hosted a video webinar presenting on the first steps of developing, running and continuing a primate conservation program. Dr. Christopher Shaffer, Rahayu Oktaviani, and Dr. Jill Pruetz presented their early program experiences establishing wild primate conservation projects to educate primatologists around the world. The running themes of the presentations included establishing community, working locally, impacting locally and preparing for the future.

The establishment of a collaborative surveillance program with indigenous hunters to characterize primate health in Southern Guyana.

The consumption of primates is integral to the traditional subsistence strategies of many Indigenous communities throughout Amazonia. Understanding the overall health of primates harvested for food in the region is critical to Indigenous food security and thus, these communities are highly invested in long-term primate population health. Here, we describe the establishment of a surveillance comanagement program among the Waiwai, an Indigenous community in the Konashen Amerindian Protected Area (KAPA). To assess primate health in the KAPA, hunters performed field necropsies on primates harvested for food and tissues collected from these individuals were analyzed using histopathology. From 2015 to 2019, hunters conducted 127 necropsies across seven species of primates. Of this sample, 82 primates (between 2015 and 2017) were submitted for histopathological screening. Our histopathology data revealed that KAPA primates had little evidence of underlying disease. Of the tissue abnormalities observed, the majority were either due to diet (e.g., hepatocellular pigment), degenerative changes resulting from aging (e.g., interstitial nephritis, myocyte lipofusion), or nonspecific responses to antigenic stimulation (renal and splenic lymphoid hyperplasia). In our sample, 7.32% of individuals had abnormalities that were consistent with a viral etiology, including myocarditis and hepatitis. Internal parasites were observed in 53.66% of individuals and is consistent with what would be expected from a free-ranging primate population. This study represents the importance of baseline data for long-term monitoring of primate populations hunted for food. More broadly, this research begins to close a critical gap in zoonotic disease risk related to primate harvesting in Amazonia, while also demonstrating the benefits of partnering with Indigenous hunters and leveraging hunting practices in disease surveillance and primate population health assessment.

Synthesis of [11C]BIIB104, an α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic-Acid-Positive Allosteric Modulator, and Evaluation of the Bio-Distribution in Non-Human Primate Brains Using Positron Emission Tomography.

The aim of this study was to measure the brain penetrance and kinetics of BIIB104, a first-in-class AMPA receptor potentiator developed for cognitive impairment associated with schizophrenia. It was recently halted in phase 2 clinical development, and there are a lack of tools to directly measure AMPA receptor engagement. To achieve this, the drug candidate was radiolabeled with carbon-11, and its brain penetrance and kinetics were measured in non-human primates via dynamic PET scans. Radiolabeling was achieved through a three-step nucleophilic [11C]cyanation reaction in one pot, resulting in the high radioactivity and radiochemical purity (>99%) of [11C]BIIB104. The study found that [11C]BIIB104 entered the non-human primate brains at 4-5% ID at peak, with a homogeneous distribution. However, a mild regional heterogeneity was observed in the thalamus. The lack of conclusive evidence for a change in regional values after BIIB104 dosing suggests that any specific binding component of BIIB104 is negligible compared to the free and non-specific components in the living brain. Overall, the study demonstrated high brain uptake with minor variability in [11C]BIIB104 distribution across various brain regions, its kinetics were consistent with those of passive diffusion, and the dominating components were the free concentration and non-specific binding. This information is valuable for understanding the potential effects and mechanisms of BIIB104 in the brain.

Unbound Brain-to-Plasma Partition Coefficient, Kp,uu,brain-a Game Changing Parameter for CNS Drug Discovery and Development.

PURPOSE: More than 15 years have passed since the first description of the unbound brain-to-plasma partition coefficient (Kp,uu,brain) by Prof. Margareta Hammarlund-Udenaes, which was enabled by advancements in experimental methodologies including cerebral microdialysis. Since then, growing knowledge and data continue to support the notion that the unbound (free) concentration of a drug at the site of action, such as the brain, is the driving force for pharmacological responses. Towards this end, Kp,uu,brain is the key parameter to obtain unbound brain concentrations from unbound plasma concentrations. METHODS: To understand the importance and impact of the Kp,uu,brain concept in contemporary drug discovery and development, a survey has been conducted amongst major pharmaceutical companies based in Europe and the USA. Here, we present the results from this survey which consisted of 47 questions addressing: 1) Background information of the companies, 2) Implementation, 3) Application areas, 4) Methodology, 5) Impact and 6) Future perspectives. RESULTS AND CONCLUSIONS: From the responses, it is clear that the majority of the companies (93%) has established a common understanding across disciplines of the concept and utility of Kp,uu,brain as compared to other parameters related to brain exposure. Adoption of the Kp,uu,brain concept has been mainly driven by individual scientists advocating its application in the various companies rather than by a top-down approach. Remarkably, 79% of all responders describe the portfolio impact of Kp,uu,brain implementation in their companies as 'game-changing'. Although most companies (74%) consider the current toolbox for Kp,uu,brain assessment and its validation satisfactory for drug discovery and early development, areas of improvement and future research to better understand human brain pharmacokinetics/pharmacodynamics translation have been identified.

Near-UV Water Splitting by Cu, Ni, and Co Complexes in the Gas Phase.

(2,2'-Bipyridine)M═O+ ions (M = Cu, Ni, Co) were generated by collision-induced dissociation and near-UV photodissociation of readily available [(2,2'-bipyridine)MII(NO3)]+ ions in the gas phase, and their structure was confirmed by ion-molecule reactions combined with isotope labeling. Upon storage in a quadrupole ion trap, the (2,2'-bipyridine)M═O+ ions spontaneously added water, and the formed [(2,2'-bipyridine)M═O + H2O]+ complexes eliminated OH upon further near-UV photodissociation. This reaction sequence can be accomplished at a single laser wavelength in the range of 260-340 nm to achieve stoichiometric homolytic cleavage of gaseous water. Structures, spin states, and electronic excitations of the metal complexes were characterized by ion-molecule reactions using 2H and 18O labeling, photodissociation action spectroscopy, and density functional theory calculations.

Sustainability and comanagement of subsistence hunting in an indigenous reserve in Guyana.

Although hunting is a key component of subsistence strategies of many Amazonians, it is also one of the greatest threats to wildlife. Because indigenous reserves comprise over 20% of Amazonia, effective conservation often requires that conservation professionals work closely with indigenous groups to manage resource use. We used hunter-generated harvesting data in spatially explicit biodemographic models to assess the sustainability of subsistence hunting of indigenous Waiwai in Guyana. We collected data through a hunter self-monitoring program, systematic follows of hunters, and semistructured interviews. We used these data to predict future densities of 2 indicator species, spider monkeys (Ateles paniscus) and bearded sakis (Chiropotes sagulatus), under different scenarios of human population expansion and changing hunting technology. We used encounter rates from transect surveys and hunter catch-per-unit effort (CPUE) to validate model predictions. Paca (Cuniculus paca) (198 /year), Currosaw (Crax alector) (168), and spider monkey (117) were the most frequently harvested species. Predicted densities of spider monkeys were statistically indistinguishable from empirically derived transect data (Kolmogorov-Smirnov D = 0.67, p = 0.759) and CPUE (D = 0.32, p = 1.000), demonstrating the robustness of model predictions. Ateles paniscus and C. sagulatus were predicted to be extirpated from <13% of the Waiwai reserve in 20 years, even under the most intensive hunting scenarios. Our results suggest Waiwai hunting is currently sustainable, primarily due to their low population density and use of bow and arrow. Continual monitoring is necessary, however, particularly if human population increases are accompanied by a switch to shotgun-only hunting. We suggest that hunter self-monitoring and biodemographic modeling can be used effectively in a comanagement approach in which indigenous parabiologists continuously provide hunting data that is then used to update model parameters and validate model predictions.

Quantitative projection of human brain penetration of the H3 antagonist PF-03654746 by integrating rat-derived brain partitioning and PET receptor occupancy.

1. Unbound brain drug concentration (Cb,u), a valid surrogate of interstitial fluid drug concentration (CISF), cannot be directly determined in humans, which limits accurately defining the human Cb,u:Cp,u of investigational molecules. 2. For the H3R antagonist (1R,3R)-N-ethyl-3-fluoro-3-[3-fluoro-4-(pyrrolidin-1-lmethyl)phenyl]cyclobutane-1-carboxamide (PF-03654746), we interrogated Cb,u:Cp,u in humans and nonhuman primate (NHP). 3. In rat, PF-03654746 achieved net blood-brain barrier (BBB) equilibrium (Cb,u:Cp,u of 2.11). 4. In NHP and humans, the PET receptor occupancy-based Cp,u IC50 of PF-03654746 was 0.99 nM and 0.31 nM, respectively, which were 2.1- and 7.4-fold lower than its in vitro human H3 Ki (2.3 nM). 5. In an attempt to understand this higher-than-expected potency in humans and NHP, rat-derived Cb,u:Cp,u of PF-03654746 was integrated with Cp,u IC50 to identify unbound (neuro) potency of PF-03654746, nIC50. 6. The nIC50 of PF-03654746 was 2.1 nM in NHP and 0.66 nM in human which better correlated (1.1- and 3.49-fold lower) with in vitro human H3 Ki (2.3 nM). 7. This correlation of the nIC50 and in vitro hH3 Ki suggested the translation of net BBB equilibrium of PF-03654746 from rat to NHP and humans, and confirmed the use of Cp,u as a reliable surrogate of Cb,u. 8. Thus, nIC50 quantitatively informed the human Cb,u:Cp,u of PF-03654746.

Student Preparation for PGY1 Residency Training by US Colleges of Pharmacy: Survey of the Residency Program Director Perspective.

Purpose: To evaluate current residents' level of preparation by US colleges of pharmacy for postgraduate year 1 (PGY1) residency training from the perspective of residency program directors (RPDs). Methods: RPDs were asked in an electronic survey questionnaire to rate PGY1 pharmacy residents' abilities in 4 domains: communication, clinical knowledge, interpersonal/time-management skills, and professionalism/leadership. Results: One hundred ninety-seven RPDs of the American Society of Health-System Pharmacists (ASHP)-accredited PGY1 programs completed the survey. The majority of RPDs strongly agreed or agreed that residents were prepared as students to effectively communicate both verbally and nonverbally, were able to appropriately respond to drug inquiries using drug resources and literature searches, and consistently displayed professionalism. Respondents were more likely to disagree or give a neutral response when asked about residents' understanding of biostatistics and their ability to provide enteral and parenteral nutritional support for patients. Conclusion: Overall, RPDs agreed that residents were prepared to perform the majority of the tasks of each of the 4 domains assessed in this survey relating to PGY1 training. RPDs may use the results of this survey to provide additional support for their residents in the areas in which residents lack adequate preparation, while colleges of pharmacy may focus on incorporating more time in their curriculum for certain areas to better prepare their students for residency training.

Mixed-species associations in cuxiús (genus Chiropotes).

Polyspecific or mixed-species associations, where two or more species come together to forage and travel as a unit, have been reported in many primate species. These associations appear to offer a number of benefits to the species involved including increased foraging efficiency and decreased risk of predation. While several researchers have suggested that cuxiús (genus Chiropotes) form mixed-species associations, previous studies have not identified the circumstances under which cuxiús form associations or whether they form associations more often than would be expected by chance. Here we present data on the formation of mixed-species associations by four species of cuxiús at eight different sites in Brazil, Suriname, and Guyana. We analyzed data from two of the study sites, (Biological Dynamics of Forest Fragments Project (BDFFP), Brazil and the Upper Essequibo Conservation Concession (UECC), Guyana, to assess whether associations occurred more than would be expected by chance encounters and identify the factors influencing their formation. Cuxiús showed a high degree of inter-site variation in the frequency of time spent in association (ranging from 2 to 26% of observation time) and duration of associations (mean duration from 22 min to 2.5 hr). Sapajus apella was the most common association partner at most sites. At BDFFP, cuxiús formed associations more frequently but not for longer duration than expected by chance. For much of the year at UECC, associations were not more frequent or longer than chance. However, during the dry season, cuxiús formed associations with S. apella significantly more often and for longer duration than predicted by chance. Cuxiús at UECC formed associations significantly more often when in smaller subgroups and when foraging for insects, and alarm called significantly less frequently during associations. We suggest cuxiús form mixed-species associations at some sites as an adaptive strategy to decrease predation risk and/or increase foraging efficiency.

Geographic comparison of plant genera used in frugivory among the pitheciids Cacajao, Callicebus, Chiropotes, and Pithecia.

Pitheciids are known for their frugivorous diets, but there has been no broad-scale comparison of fruit genera used by these primates that range across five geographic regions in South America. We compiled 31 fruit lists from data collected from 18 species (three Cacajao, six Callicebus, five Chiropotes, and four Pithecia) at 26 study sites in six countries. Together, these lists contained 455 plant genera from 96 families. We predicted that 1) closely related Chiropotes and Cacajao would demonstrate the greatest similarity in fruit lists; 2) pitheciids living in closer geographic proximity would have greater similarities in fruit lists; and 3) fruit genus richness would be lower in lists from forest fragments than continuous forests. Fruit genus richness was greatest for the composite Chiropotes list, even though Pithecia had the greatest overall sampling effort. We also found that the Callicebus composite fruit list had lower similarity scores in comparison with the composite food lists of the other three genera (both within and between geographic areas). Chiropotes and Pithecia showed strongest similarities in fruit lists, followed by sister taxa Chiropotes and Cacajao. Overall, pitheciids in closer proximity had more similarities in their fruit list, and this pattern was evident in the fruit lists for both Callicebus and Chiropotes. There was no difference in the number of fruit genera used by pitheciids in habitat fragments and continuous forest. Our findings demonstrate that pitheciids use a variety of fruit genera, but phylogenetic and geographic patterns in fruit use are not consistent across all pitheciid genera. This study represents the most extensive examination of pitheciid fruit consumption to date, but future research is needed to investigate the extent to which the trends in fruit genus richness noted here are attributable to habitat differences among study sites, differences in feeding ecology, or a combination of both.

UV/Vis Action Spectroscopy and Structures of Tyrosine Peptide Cation Radicals in the Gas Phase.

We report the first application of UV/Vis photodissociation action spectroscopy for the structure elucidation of tyrosine peptide cation radicals produced by oxidative intramolecular electron transfer in gas-phase metal complexes. Oxidation of Tyr-Ala-Ala-Ala-Arg (YAAAR) produces Tyr-O radicals by combined electron and proton transfer involving the phenol and carboxyl groups. Oxidation of Ala-Ala-Ala-Tyr-Arg (AAAYR) produces a mixture of cation radicals involving electron abstraction from the Tyr phenol ring and N-terminal amino group in combination with hydrogen-atom transfer from the Cα positions of the peptide backbone.

Cluster M mycobacteriophages Bongo, PegLeg, and Rey with unusually large repertoires of tRNA isotypes.

UNLABELLED: Genomic analysis of a large set of phages infecting the common host Mycobacterium smegmatis mc(2)155 shows that they span considerable genetic diversity. There are more than 20 distinct types that lack nucleotide similarity with each other, and there is considerable diversity within most of the groups. Three newly isolated temperate mycobacteriophages, Bongo, PegLeg, and Rey, constitute a new group (cluster M), with the closely related phages Bongo and PegLeg forming subcluster M1 and the more distantly related Rey forming subcluster M2. The cluster M mycobacteriophages have siphoviral morphologies with unusually long tails, are homoimmune, and have larger than average genomes (80.2 to 83.7 kbp). They exhibit a variety of features not previously described in other mycobacteriophages, including noncanonical genome architectures and several unusual sets of conserved repeated sequences suggesting novel regulatory systems for both transcription and translation. In addition to containing transfer-messenger RNA and RtcB-like RNA ligase genes, their genomes encode 21 to 24 tRNA genes encompassing complete or nearly complete sets of isotypes. We predict that these tRNAs are used in late lytic growth, likely compensating for the degradation or inadequacy of host tRNAs. They may represent a complete set of tRNAs necessary for late lytic growth, especially when taken together with the apparent lack of codons in the same late genes that correspond to tRNAs that the genomes of the phages do not obviously encode. IMPORTANCE: The bacteriophage population is vast, dynamic, and old and plays a central role in bacterial pathogenicity. We know surprisingly little about the genetic diversity of the phage population, although metagenomic and phage genome sequencing indicates that it is great. Probing the depth of genetic diversity of phages of a common host, Mycobacterium smegmatis, provides a higher resolution of the phage population and how it has evolved. Three new phages constituting a new cluster M further expand the diversity of the mycobacteriophages and introduce novel features. As such, they provide insights into phage genome architecture, virion structure, and gene regulation at the transcriptional and translational levels.

Drug-induced Skin Lesions in Cynomolgus Macaques Treated with Metabotropic Glutamate Receptor 5 (mGluR5) Negative Allosteric Modulators.

Three orally administered metabotropic glutamate receptor 5 (mGluR5) negative allosteric modulators caused skin lesions consistent with delayed type-IV hypersensitivity in cynomolgus macaques in 2- and 12-week toxicity studies. Several monkeys developed macroscopic skin lesions in multiple locations after 8 to 9 days of dosing; the most prominent effects involved the genital region of males and generalized erythema occurred in both sexes. Microscopic lesions occurred in both clinically affected and unaffected areas and were characterized by lymphocytic interface inflammation, subepidermal bullae, and individual keratinocyte vacuolation/necrosis. In the 12-week study, clinical effects in 2 animals resolved with continued dosing, whereas in others the inflammatory process progressed with 1 female exhibiting systemic lymphocytic inflammation in multiple tissues. The inflammatory infiltrate consisted of CD3 and CD4 positive T lymphocytes with minimal CD68 positive macrophages and only rare CD8 positive T lymphocytes. A subset of animals given a dosing holiday was subsequently rechallenged with similar lesions developing but with a more rapid clinical onset. These skin lesions were consistent with type-IV delayed hypersensitivity with some features comparable to bullous drug eruptions in humans. A relationship between these findings and the intended mode of action for these compounds could not be ruled out, given the occurrence across different chemotypes.

Serine effects on collision-induced dissociation and photodissociation of peptide cation radicals of the z+• -type.

The serine residue displays specific effects on the dissociations of peptide fragment cation-radicals of the z+• type which are produced by electron transfer dissociation. Energy-resolved collision-induced dissociation (ER-CID), time-resolved infrared multiphoton dissociation (TR-IRMPD), and single-photon UV photodissociation at 355 nm revealed several competitive dissociation pathways consisting of loss of OH radical, water, and backbone cleavages occurring at N-terminal and C-terminal positions relative to the serine residue. The activation modes using slow-heating and UV photon absorption resulted in different relative intensities of fragment ions. This indicated that the dissociations proceeded through several channels with different energy-dependent kinetics. The experimental data were interpreted with the help of electron structure calculations that provided fully optimized structures and relative energies for cis and trans amide isomers of the z4+• ions as well as isomerization, dissociation, and transition state energies. UV photon absorption by the z4+• ions was due to Cα-radical amide groups created by ETD that provided a new chromophore absorbing at 355 nm.

Spatial foraging in free ranging bearded sakis: traveling salesmen or Lévy Walkers?

According to optimal foraging theory and most current models of primate socioecology, primate foraging involves a series of decisions concerning when is the most optimal time to leave a food patch, how to travel to the next patch in an efficient manner, and how to minimize the time and distance traveled to all patches throughout the course of the day. In this study, I assess how bearded sakis solve these challenges by presenting data on their patch use, distance minimization, and by comparing their movements with non-deterministic foraging patterns. The study group, composed of 38 ± 15 individuals, fed significantly longer in higher quality patches (quality defined by patch size and productivity) and in those that contained ripe fruit pulp. However, group size was not a significant predictor of patch occupancy. Bearded sakis traveled relatively directly between food patches, sometimes over distances > 300 m. In addition, they chose the optimal daily path among all patches visited on 9 of 17 occasions, and on average traveled only 21% more than the least distance route. Bearded saki step lengths were consistent with a Brownian rather than a Lévy Walk pattern while waiting times were consistent with a Lévy pattern. However, the distribution of their turning angles indicated a high degree of directional persistence between patches. These results suggest that bearded sakis exploit food patches that are randomly distributed spatially but heterogenous in patch quality. They appear to encode the locations of high quality food patches and minimize travel between them, despite opportunistically feeding from more abundant and randomly distributed, lower quality patches en route.

Positive allosteric modulation of AMPA receptors from efficacy to toxicity: the interspecies exposure-response continuum of the novel potentiator PF-4778574.

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) positive allosteric modulation (i.e., "potentiation") has been proposed to overcome cognitive impairments in schizophrenia, but AMPAR overstimulation can be excitotoxic. Thus, it is critical to define carefully a potentiator's mechanism-based therapeutic index (TI) and to determine confidently its translatability from rodents to higher-order species. Accordingly, the novel AMPAR potentiator N-{(3R,4S)-3-[4-(5-cyano-2-thienyl)phenyl]tetrahydro-2H-pyran-4-yl}propane-2-sulfonamide (PF-4778574) was characterized in a series of in vitro assays and single-dose animal studies evaluating AMPAR-mediated activities related to cognition and safety to afford an unbound brain compound concentration (Cb,u)-normalized interspecies exposure-response relationship. Because it is unknown which AMPAR subtype(s) may be selectively potentiated for an optimal TI, PF-4778574 binding affinity and functional potency were determined in rodent tissues expected to express a native mixture of AMPAR subunits and their associated proteins to afford composite pharmacological values. Functional activity was also quantified in recombinant cell lines stably expressing human GluA2 flip or flop homotetramers. Procognitive effects of PF-4778574 were evaluated in both rat electrophysiological and nonhuman primate (nhp) behavioral models of pharmacologically induced N-methyl-d-aspartate receptor hypofunction. Safety studies assessed cerebellum-based AMPAR activation (mouse) and motor coordination disruptions (mouse, dog, and nhp), as well as convulsion (mouse, rat, and dog). The resulting empirically derived exposure-response continuum for PF-4778574 defines a single-dose-based TI of 8- to 16-fold for self-limiting tremor, a readily monitorable clinical adverse event. Importantly, the Cb,u mediating each physiological effect were highly consistent across species, with efficacy and convulsion occurring at just fractions of the in vitro-derived pharmacological values.

Gis analysis of patch use and group cohesiveness of bearded sakis (chiropotes sagulatus) in the upper essequibo conservation concession, Guyana.

This study examines how northern bearded sakis (Chiropotes sagulatus) in Guyana adjust group cohesiveness according to the distribution and quality of food patches. I introduce a GIS based method for quantifying food patch quality and how it relates to bearded saki group spread and group size. While the concept of food patch is central to most models of primate socioecology, defining what constitutes a patch has been notoriously problematic in primate studies. In addition, researchers have struggled to quantify group spread and group cohesiveness. Advances in spatial analysis software in the last decade now allow primate researchers to better quantify these variables. Group spread in bearded sakis was not significantly greater in lower quality patches and sakis were not more spread out during feeding than during other activities. However, the study group was significantly less spread out during social behavior. Bearded saki group size was significantly correlated with both monthly fruit abundance and patch quality. In fact, mean daily patch quality explained ∼40% of the variation in foraging party size. These results suggest that bearded sakis may rely on a highly fluid social structure to mitigate the effects of intragroup feeding competition while living in large groups. Sakis do not adjust group spread on a patch-by-patch basis but rather fission into smaller foraging parties when resources become scarce seasonally and patch quality is low. This study shows that GIS is a powerful tool for modeling the relationship between group cohesiveness and resource quality and distribution.

Feeding Ecology of northern bearded sakis (Chiropotes sagulatus) in Guyana.

Bearded sakis (genus Chiropotes) are among the most highly specialized primate seed predators. However, long-term studies of the genus in continuous forests, with a full community of sympatric primates, are rare. Here I present data on monthly variation in the diet of Chiropotes sagulatus from a long-term study in a continuous forest in Guyana. Bearded sakis had an extremely diverse diet, exploiting more than 175 species of plants. Consistent with their highly specialized dental morphology for seed eating, seeds made up 75% of the annual diet. Sakis exploited a wide variety of mechanically protected fruits and often exploited the same plant species for more than 3 months. They consumed a high percentage of seeds in all months and seed consumption was significantly correlated with fruit abundance. When fruit became scarcer, sakis consumed a higher percentage of non-seed food items, including insects, mature fruit, and flowers. Insects were especially important during the leanest months, making up almost 40% of feeding time. Bearded saki dietary diversity (in terms of plant species) showed little variability across months. These results confirm sakis to be highly specialized seed predators. Sakis preferentially consume seeds when they are available. However, when seeds become scarce, sakis become generalists, supplementing their diet with mature fruit, insects, and flowers. The ability of bearded sakis to consume a diversity of highly abundant plant species, fruit in several stages of maturity, and a variety of different types of resources buffers them from the detrimental effects of resource scarcity.

GB1 hairpin kinetics: capturing the folding pathway with molecular dynamics, replica exchange and optimal dimensionality reduction.

We have performed molecular dynamics (MD) and replica-exchange (REMD) simulations of folding of the GB1 hairpin peptide in aqueous solution. REMD results were consistent with a cooperative zipper folding model. 120 µs MD trajectories at 320 K yielded relaxation times of 1.8 µs and 100 ns, with the slower assigned to global folding. The MD folding/unfolding transitions also followed the cooperative zipper model, specifying nucleation at the central turn followed by consecutive hydrogen bond formation. Formation of hydrogen bonds and hydrophobic contacts were highly correlated. Coarse-grained kinetic models constructed with the Optimal Dimensionality Reduction (ODR) approach found a folding time of 3.3 µs and unfolding time of 4.0 µs. Additionally, relaxation times in the 130-170 ns range could be assigned to formation of the transition state and off-path intermediates. The unfolded state was the most highly populated and, significantly, most heterogenous, assembling the largest number of microstates, primarily composed of extended and turn structures. The folded state was also heterogenous, but a to a lesser degree, involving the fully folded and partially folded in-register hairpins at early stages of the zipper pathway. The transition state corresponded to the nucleated hairpin, with central turn and first beta-sheet hydrogen bond, while the off-path intermediates were off-register partial hairpins. Our simulation results were in excellent agreement with experimental data on folded fraction, relaxation time and folding mechanism. The new findings from this work suggest a highly cooperative zipper folding mechanism, nascent hairpin transition state and ∼100 ns relaxation related to intermediate formation.Communicated by Ramaswamy H. Sarma.