5 research outputs found
Charge Balancing of Model Gold-Nanoparticle-Peptide Conjugates Controlled by the Peptide’s Net Charge and the Ligand to Nanoparticle Ratio
Gold
nanoparticles (AuNPs) covalently bound to biomolecules, termed bioconjugates, are highly relevant for biological applications
like drug targeting or bioimaging. Here, the net charge of the bioconjugate
is one key parameter affecting biocompatibility and cell membrane
interaction. However, when negatively charged AuNPs are conjugated
to positively charged biomolecules, resulting charge compensation
compromises the stability of the conjugates. In this work, laser-generated
negatively charged AuNPs exhibiting a bare surface were used as a
model and separately conjugated to cell penetrating peptides (CPPs)
carrying different positive net charges. Occurring charge compensation
leads to two regimes where stable bioconjugates are obtained on both
sides of the bioconjugate’s isoelectric point. These regimes
can be controlled by the peptide’s net charge. Generally, increasing
the peptide’s net charges yields stable positively charged
bioconjugates with decreased surface coverages. To demonstrate the
compatibility of the bioconjugates in bioapplications, long-term stability
measurements were performed. Furthermore, the uptake by live mammalian
cells was investigated with multiphoton microscopy using the luminescence
of the AuNP–peptide conjugates. The results for our model system
of laser-generated AuNPs and CPPs show that a precise tuning of conjugate
properties is possible. They can be transferred to other oppositely
charged nanoparticle−ligand systems, avoiding occurrence of
charge compensation with defined ligand load
Vigorous Dynamics Underlie a Stable Population of the Endangered Snow Leopard Panthera uncia in Tost Mountains, South Gobi, Mongolia
Population monitoring programmes and estimation of vital rates are key to understanding the mechanisms of population growth, decline or stability, and are important for effective conservation action. We report, for the first time, the population trends and vital rates of the endangered snow leopard based on camera trapping over four years in the Tost Mountains, South Gobi, Mongolia. We used robust design multi-season mark-recapture analysis to estimate the trends in abundance, sex ratio, survival probability and the probability of temporary emigration and immigration for adult and young snow leopards. The snow leopard population remained constant over most of the study period, with no apparent growth (lambda = 1.08+-20.25). Comparison of model results with the "known population'' of radio-collared snow leopards suggested high accuracy in our estimates. Although seemingly stable, vigorous underlying dynamics were evident in this population, with the adult sex ratio shifting from being male-biased to female-biased (1.67 to 0.38 males per female) during the study. Adult survival probability was 0.82 (SE+-0.08) and that of young was 0.83 (SE+-0.15) and 0.77 (SE+-0.2) respectively, before and after the age of 2 years. Young snow leopards showed a high probability of temporary emigration and immigration (0.6, SE +-0.19 and 0.68, SE +-0.32 before and after the age of 2 years) though not the adults (0.02 SE+-0.07). While the current female-bias in the population and the number of cubs born each year seemingly render the study population safe, the vigorous dynamics suggests that the situation can change quickly. The reduction in the proportion of male snow leopards may be indicative of continuing anthropogenic pressures. Our work reiterates the importance of monitoring both the abundance and population dynamics of species for effective conservation