Effect of redox-responsive DTSSP crosslinking on poly(l-lysine)-grafted-poly(ethylene glycol) nanoparticles for delivery of proteins

Therapeutic proteins are utilized in a variety of clinical applications, but side effects and rapid in vivo clearance still present hurdles. An approach that addresses both drawbacks is protein encapsulation within in a polymeric nanoparticle, which is effective but introduces the additional challenge of destabilizing the nanoparticle shell in clinically relevant locations. This study examined the effects of crosslinking self-assembled poly(l -lysine)-grafted-poly(ethylene glycol) nanoparticles with redox-responsive 3,3′-dithiobis(sulfosuccinimidyl propionate) (DTSSP) to achieve nanoparticle destabilization in a reductive environment. The polymer-protein nanoparticles (DTSSP NPs) were formed through electrostatic self-assembly and crosslinked with DTSSP, which contains a glutathione-reducible disulfide. As glutathione is upregulated in various cancers, DTSSP NPs could display destabilization within cancer cells. A library of DTSSP NPs was formed with varying copolymer to protein (C:P) and crosslinker to protein (X:P) mass ratios and characterized by size and encapsulation efficiency. DTSSP NPs with a 7:1 C:P ratio and 2:1 X:P ratio were further characterized by stability in the presence proteases and reducing agents. DTSSP NPs fully encapsulated the model protein and displayed 81% protein release when incubated with 5 mM dithiothreitol for 12 hr. This study contributes to understanding stimulus-responsive crosslinking of polymeric nanoparticles and could be foundational to clinical administration of therapeutic proteins.     

Conformations of blood group H-active oligosaccharides of ovarian cyst mucins

Spectroscopic data and conformational energy calculations are reported for eight oligosaccharides from ovarian cyst mucins and from human milk, the nonreducing terminals of which have fucose (α1 → 2)galactose linked either (β1 → 3) (type I) or (β1 → 4)(type II) to N-acetylglucosamine or in (β1 → 3) linkage to galactosaminitol. The fully assigned proton nmr spectra are reported along with nuclear Overhauser enhancement (NOE) data. Amide proton coupling constants and vacuum-uv CD spectra provide information on the amide plane orientation and amide environment. Our results imply that the fucosidic dihedral angles are similar for all three cases and that the substantial differences in the chemical shifts of the fucosyl protons of type I, type II, and 3-ol chains result from different perturbations by the amide group of the residue to which the β-galactose is linked. Stereopair diagrams of conformational models for both type I and II H chains are presented that are consistent with NOE, coupling constants, conformational energy calculations, and the CD data. While the temperature dependence of the observed NOE of penta- and hexasaccharides indicates that their rotational correlation times are strongly temperature dependent, we conclude that the conformations are essentially independent of temperature.     

Darting and marking techniques for an arboreal forest monkey,Cercopithecus ascanius

Techniques are described for capturing and marking redtail monkeys (Cercopithecus ascanius). An air-powered darting rifle and syringe darts loaded with a Ketamine-Rompun mixture were used for capture. Ketamine was used for maintaining anesthesia. Monkeys were darted 48 times and captured 27 times. In 24 of the 27 captures, the monkeys were released unharmed. Adult males were marked with radiotransmitters attached to collars of nylon webbing. Females received nylon webbing collars with colorcoded plastic washers for identification.     

Can We Accurately Characterize Wildlife Resource Use When Telemetry Data Are Imprecise?

ABSTRACT Telemetry data have been widely used to quantify wildlife habitat relationships despite the fact that these data are inherently imprecise. All telemetry data have positional error, and failure to account for that error can lead to incorrect predictions of wildlife resource use. Several techniques have been used to account for positional error in wildlife studies. These techniques have been described in the literature, but their ability to accurately characterize wildlife resource use has never been tested. We evaluated the performance of techniques commonly used for incorporating telemetry error into studies of wildlife resource use. Our evaluation was based on imprecise telemetry data (mean telemetry error = 174 m, SD = 130 m) typical of field-based studies. We tested 5 techniques in 10 virtual environments and in one real-world environment for categorical (i.e., habitat types) and continuous (i.e., distances or elevations) rasters. Technique accuracy varied by patch size for the categorical rasters, with higher accuracy as patch size increased. At the smallest patch size (1 ha), the technique that ignores error performed best on categorical data (0.31 and 0.30 accuracy for virtual and real data, respectively); however, as patch size increased the bivariate-weighted technique performed better (0.56 accuracy at patch sizes >31 ha) and achieved complete accuracy (i.e., 1.00 accuracy) at smaller patch sizes (472 ha and 1,522 ha for virtual and real data, respectively) than any other technique. We quantified the accuracy of the continuous covariates using the mean absolute difference (MAD) in covariate value between true and estimated locations. We found that average MAD varied between 104 m (ignore telemetry error) and 140 m (rescale the covariate data) for our continuous covariate surfaces across virtual and real data sets. Techniques that rescale continuous covariate data or use a zonal mean on values within a telemetry error polygon were significantly less accurate than other techniques. Although the technique that ignored telemetry error performed best on categorical rasters with smaller average patch sizes (i.e., ≤31 ha) and on continuous rasters in our study, accuracy was so low that the utility of using point-based approaches for quantifying resource use is questionable when telemetry data are imprecise, particularly for small-patch habitat relationships.     

Digest: How do nonnative frugivorous birds adapt to life in O'ahu?*

Species adapt to the selective pressures of novel environments. Here, Gleditsch and Sperry tested whether four nonnative frugivorous bird species on the Hawaiian island of O'ahu diverged morphologically from their ancestral populations. They found that all four species significantly diverged from populations in their native ranges, with a general trend of smaller body size and larger bills. These differences were likely due to a combination of adaptive and nonadaptive processes.     

Tabtoxinine-beta-Lactam Transport into Cultured Corn Cells : Uptake via an Amino Acid Transport System

Tabtoxinine-β-lactam (T-β-L), a unique amino acid, is a toxin produced by several closely related pathovars of Pseudomonas syringae. These chlorosis-inducing pathogens establish themselves in the apoplastic space of their hosts where they release the toxin. We have examined the transport of T-β-L into cultured corn (Zea mays cv Black Mexican) cells using [¹⁴C]T-β-L. The pH optimum of the uptake of the toxin was between 4.0 and 5.5 pH units. Toxin uptake was inhibited by the protonophore, carbonyl cyanide m-chlorophenyl hydrazone, and by the sulfhydryl re-agent, N-ethylmaleimide. Tabtoxinine-β-lactam transport exhibited saturation kinetics that were described by the Michaelis-Menton equation for toxin concentrations of 1 millimolar and less. However, the transport of toxin in concentrations greater than 1 millimolar was not described by Michaelis-Menten kinetics. Glutamate and alanine exhibited similar transport kinetics with a transition to non-Michaelis-Menten kinetics when the amino acid concentration exceeded 1 millimolar. Hill numbers for glutamate, alanine, and T-β-L ranged from 0.6 to 0.8. Methionine, alanine, tyrosine, glutamine, glutamate, and arginine were inhibitors of toxin transport. Alanine was a competitive inhibitor of the transport of T-β-L and of glutamate. The data are consistent with T-β-L being transported into the plant cell through an amino acid transport system.     

Comparison by 1H-nmr spectroscopy of the conformation of the 2600 dalton antifreeze glycopeptide of polar cod with that of the high molecular weight antifreeze glycoprotein

The antifreeze glycopeptide (AFGP-8) from polar cod, B. saida, is a 14-amino acid polypeptide having alternating glycotripeptide sequences of Ala-[Gal(β1 → 3)GalNAc(β1 → O)]-Thr-Pro and Ala-[Gal(β1 → 3)GalNAc(β1 → O)]-Thr-Ala, with alanyl residues at amino and carboxy terminals. Conformational studies of AFGP-8 have been carried out by ¹H-nmr and empirical energy calculations to investigate the difference in its antifreeze behavior from that of the more active high-molecular weight AFGP 1-4 of P. borchgrevinki. The ¹H-nmr spectra, including the resonances of the exchangeable amide protons, were assigned by two-dimensional correlated spectroscopy (COSY), one-dimensional difference decoupling, and nuclear Overhauser effect (NOE) measurements. For the four threonyl residues, the amide proton coupling constants and the small coupling constants between H^α and H^β indicate similar conformations, despite significant chemical shift differences. The strong NOE between the α protons and the amide protons of the residue following together with large temperature coefficients of chemical shifts, indicate an extended conformation not consisting of α-helix, turns or bends. Energy computations indicate several low-energy conformations consistent with the observed coupling constants for ?. Among these, a left-handed helical conformation with three repeating residues per turn has been proposed, which is in accordance with the observed NOE between the methyl group of the α-GalNAc and Ala H^βs. While the observed Overhauser effects in the threonyl side chain suggest a certain amount of conformational averaging, the effect involving the acetmido methyl of α-GalNAc and H^βs of Ala indicate that it as is a major conformer. In view of the close similarity between the conformations of AFGP-8 and the more active antifreeze polymer, AFGP 1-4, we propose that the difference in their activities is due to the length of the regular repeating structure with glycosylation at every third amino acid residue, and not due to any fundamental difference in their conformations.