- Pharmaceutical design of protein formulations aims at maximum efficiency (protein concentration) and minimum viscosity. Therefore, it is important to know the nature of protein-protein interactions and their influence on Bio Med Frontiers viscosity.
- In this work, we investigated the dependence of the viscosity of BSA in an aqueous 20 mM acetate buffer at pH = 4.3 on protein concentration and on temperature (5-45 °C). The viscosity of the solution increased with protein concentration and was 230% higher than the viscosity of the protein-free formulation at 160 mg/mL.
- The viscosity decreased by almost 60% in the temperature range from 5 to 45 °C. The agreement of the modified Arrhenius theory with experiment was quantitative, whereas a hard-sphere model provided only a qualitative description of the experimental results.
- We also investigated the viscosity of a 100 mg/mL BSA solution as a function of the concentration of added low molecular weight salts (LiCl, NaCl, KCl, RbCl, CsCl, NaBr, NaI) in the range of salt concentrations up to 1.75 mol/L. In addition, the particle size and zeta potential of BSA-salt mixtures were determined for solutions containing 0.5 mol/L salt.
The trends with respect to the different anions followed a direct Hofmeister series (Cl– > Br– > I–), whereas for cations in the case of viscosity the indirect Hofmeister series was observed (Li+ > Na+ > K+ > Rb+ > Cs+), but the values of particle sizes and zeta potential did not show cation-specific effects. Since the protein is positively charged at pH = 4.3, anions are more attracted to the protein surface and shield its charge, while the interaction with cations is less pronounced.
We hypothesize that salt surface charge shielding reduces protein colloidal stability and promotes protein aggregate formation.
Electronic and Optical Properties of InAs QDs Grown by MBE on InGaAs Metamorphic Buffer
- We present the optical characterization of GaAs-based InAs quantum dots (QDs) grown by molecular beam epitaxy on a digitally alloyed InGaAs metamorphic buffer layer (MBL) with gradual composition ensuring a redshift of the QD emission up to the second telecom window.
- Based on the photoluminescence (PL) measurements and numerical calculations, we analyzed the factors influencing the energies of optical transitions in QDs, among which the QD height seems to be dominating. In addition,Study polarization anisotropy of the QD emission was observed, which is a fingerprint of significant valence states mixing enhanced by the QD confinement potential asymmetry, driven by the decreased strain with increasing In content in the MBL.
- The barrier-related transitions were probed by photoreflectance, which combined with photoluminescence data and the PL temperature dependence, allowed for the determination of the carrier activation energies and the main channels of carrier loss, identified as the carrier escape to the MBL barrier.
- Eventually, the zero-dimensional character of the emission was confirmed by detecting the photoluminescence from single QDs with identified features of the confined neutral exciton and biexciton complexes via the excitation power and polarization dependences.
Site-dependent regulation of breeding success: evidence for the buffer effect in the common guillemot, a colonially-breeding seabird
Density-dependent regulation can offer resilience to wild populations experiencing fluctuations in environmental conditions because, at lower population sizes, the average quality of habitats or resources is predicted to increase. Site-dependent regulation is a mechanism whereby individuals breed at the highest quality, most successful, sites, leaving poorer quality, less successful sites vacant.
As population size increases, higher quality sites become limiting but when populations decline, lower quality sites are vacated first, offering resilience. This process is known as the ‘buffer effect’.
However, few studies have tested whether such regulation operates in populations experiencing changes in size and trend.
We used data from a population of common guillemots Uria aalge, a colonially breeding seabird, to investigate the relationship between site occupancy probability, site quality and population size and trend.
These data were collected at five sub-colonies spanning a 38-year period (1981-2018) comprising phases of population increase, decrease and recovery.
We first tested whether site quality and population size in sub-colonies explained which sites were occupied for breeding, and if this was robust to changes in sub-colony trend.
We then investigated whether disproportionate use of higher quality sites drove average site quality and breeding success across sub-colony sizes and trends.
Finally, we tested whether individuals consistently occupied higher quality sites during periods of decline and recovery.
Higher quality sites were disproportionality used when sub-colony size was smaller, resulting in higher average site quality and breeding success at lower population sizes.
This relationship was unaffected by changes in sub-colony trend. However, contrary to the predictions of the buffer effect, new sites were established at a similar rate to historically occupied sites during sub-colony decline and recovery despite being of lower quality. Our results provide support for the buffer effect conferring resilience to populations, such that average breeding success was consistently higher at lower population size during all phases of population change. However, this process was tempered by the continued establishment of new, lower quality, sites which could act to slow population recovery after periods when colony size was low.
Favorable spring conditions can buffer the impact of winter carryover effects on a key breeding decision in an Arctic-breeding seabird
The availability and investment of energy among successive life-history stages is a key feature of carryover effects. In migratory organisms, examining how both winter and spring experiences carryover to affect breeding activity is difficult due to the challenges in tracking individuals through these periods without impacting their behavior, thereby biasing results.
Using common eiders Somateria mollissima, we examined whether spring conditions at an Arctic breeding colony (East Bay Island, Nunavut, Canada) can buffer the impacts of winter temperatures on body mass and breeding decisions in birds that winter at different locations (Nuuk and Disko Bay, Greenland, and Newfoundland, Canada; assessed by analyzing stable isotopes of 13-carbon in winter-grown claw samples). Specifically, we used path analysis to examine how wintering and spring environmental conditions interact to affect breeding propensity (a key reproductive decision influencing lifetime fitness in female eiders) within the contexts of the timing of colony arrival, pre-breeding body mass (body condition), and a physiological proxy for foraging effort (baseline corticosterone).
TT Buffer (Tris-Tricine buffer) Primix powder |
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| TD8133 | Bio Basic | 1PK, 10L | 91.32 EUR |
10X Tris-Glycine Native Buffer (Transfer buffer) |
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| T8052-050 | GenDepot | 500ml | 96 EUR |
10X Tris-Glycine Native Buffer (Transfer buffer) |
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| T8052-100 | GenDepot | 2X500ml | 124.8 EUR |
10X Tris-Glycine Native Buffer (Transfer buffer) |
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| T8052-101 | GenDepot | 1L | 114 EUR |
10X Tris-Glycine Native Buffer (Transfer buffer) |
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| T8052-200 | GenDepot | 4X500ml | 153.6 EUR |
10X Tris-Glycine Native Buffer (Transfer buffer) |
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| T8052-201 | GenDepot | 2X1L | 153.6 EUR |
10X Tris-Glycine Native Buffer (Transfer buffer) |
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| T8052-401 | GenDepot | 4X1L | 198 EUR |
SM Buffer |
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| ML103-100ML | EWC Diagnostics | 1 unit | 27.98 EUR |
SM Buffer |
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| ML103-500ML | EWC Diagnostics | 1 unit | 46.58 EUR |
DF BUFFER |
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| IB47090 | IBI Scientific | 80ML | 86.87 EUR |
DF BUFFER |
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| IB47091 | IBI Scientific | 240ML | 231.66 EUR |
W1 BUFFER |
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| IB47093 | IBI Scientific | 45ML | 45.66 EUR |
W1 BUFFER |
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| IB47094 | IBI Scientific | 130ML | 82.18 EUR |
DR BUFFER |
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| IB47096 | IBI Scientific | 30ML | 69.55 EUR |
RT BUFFER |
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| IB47464 | IBI Scientific | 60ML | 52.53 EUR |
We demonstrate that warmer winter temperatures predicted lower body mass at arrival to the nesting colony, whereas warmer spring temperatures predicted earlier arrival dates and higher arrival body mass. Both higher body mass and earlier arrival dates of eider hens increased the probability that birds would initiate laying (i.e., higher breeding propensity).
However, variation in baseline corticosterone was not linked to either winter or spring temperatures, and it had no additional downstream effects on breeding propensity.Overall, we demonstrate that favorable pre-breeding conditions in Arctic-breeding common eiders can compensate for the impact that unfavorable wintering conditions can have on breeding investment, perhaps due to greater access to foraging areas prior to laying.