Human serum amyloid A protein. Behaviour in aqueous and urea-containing solutions and antibody production.
Ontology highlight
ABSTRACT:
SUBMITTER: Strachan AF
PROVIDER: S-EPMC1133438 | biostudies-other | 1989 Oct
REPOSITORIES: biostudies-other
Similar Datasets
Project description:Fluorinated surfactants are used in a wide range of applications that involve aqueous solvents incorporating various additives. The presence of organic compounds such as urea is expected to affect the self-assembly of fluorinated surfactants, however, very little is known about this. We investigated the effect of urea on the micellization in water of the common fluorinated surfactant ammonium perfluorooctanoate (APFO), and on the structure and microenvironment of the micelles that APFO forms. Addition of urea to aqueous APFO solution decreased the critical micellization concentration (CMC) and increased the counterion dissociation. The observed increase in surface area per APFO headgroup and decrease in packing density at the micelle surface suggest the localization of urea at the micelle surface in a manner that reduces headgroup repulsions. Micropolarity data further support this picture. The results presented here indicate that significant differences exist between urea effects on fluorinated surfactant and on hydrocarbon surfactant micellization in aqueous solution. For example, the CMC of sodium dodecyl sulfate (SDS) increased with urea addition, while the increase in surface area per headgroup and packing density of SDS with urea addition are much lower than those observed for APFO. This study informs fluorinated surfactant fate and transport in the environment, and also applications involving aqueous media in which urea or similar additives are present.
| S-EPMC6888096 | biostudies-literature
Project description:For realization of a wearable artificial kidney based on regeneration of a small volume of dialysate, efficient urea removal from dialysate is a major challenge. Here a potentially suitable polymeric sorbent based on phenylglyoxaldehyde (PGA), able to covalently bind urea under physiological conditions, is described. Sorbent beads containing PGA groups were obtained by suspension polymerization of either styrene or vinylphenylethan-1-one (VPE), followed by modification of the aromatic groups of poly(styrene) and poly(VPE) into PGA. It was found that PGA-functionalized sorbent beads had maximum urea binding capacities of 1.4-2.2 mmol/g and removed ∼0.6 mmol urea/g in 8 h at 37 °C under static conditions from urea-enriched phosphate-buffered saline, conditions representative of dialysate regeneration. This means that the daily urea production of a dialysis patient can be removed with a few hundred grams of this sorbent which, is an important step forward in the development of a wearable artificial kidney.
| S-EPMC7027168 | biostudies-literature
Project description:Trimethylamine N-oxide (TMAO) stabilizes protein structures, whereas urea destabilizes proteins, and their opposing effects can be counteracted at a 1:2 ratio of TMAO to urea. To investigate how they affect solution dynamics, molecular dynamics simulations have been carried out for aqueous solutions of TMAO and urea at different concentrations. In the binary solutions, urea mainly slows the diffusion of waters that are hydrogen bonded to it (i.e., hydration water), whereas TMAO dramatically slows the diffusion of both hydration water and bulk water because of long-lived TMAO-water hydrogen bonds. In the ternary solutions, because TMAO decreases the diffusion rate of bulk water, the lifetimes of not only water-water but also urea-water hydrogen bonds increase. In addition, the constant forming and breaking of short lifetime hydrogen bonds between urea and water appears to impart energy into the bulk, whereas the long lifetime hydrogen bonds between TMAO and water slows down the bulk, resulting in the compensating effects on bulk water in the ternary solution. This suggests that the counteracting effects of TMAO on urea denaturation may be both to make longer lived hydrogen bonds to water and to counter the energizing effects of urea on bulk water.
| S-EPMC7085122 | biostudies-literature
Project description:Perovskite semiconductors have emerged as competitive candidates for photovoltaic applications due to their exceptional optoelectronic properties. However, the impact of moisture instability on perovskite films is still a key challenge for perovskite devices. While substantial effort is focused on preventing moisture interaction during the fabrication process, it is demonstrated that low moisture sensitivity, enhanced crystallization, and high performance can actually be achieved by exposure to high water content (up to 25 vol%) during fabrication with an aqueous-containing perovskite precursor. The perovskite solar cells fabricated by this aqueous method show good reproducibility of high efficiency with average power conversion efficiency (PCE) of 18.7% and champion PCE of 20.1% under solar simulation. This study shows that water-perovskite interactions do not necessarily negatively impact the perovskite film preparation process even at the highest efficiencies and that exposure to high contents of water can actually enable humidity tolerance during fabrication in air.
| S-EPMC5770683 | biostudies-literature
Project description:Hybridization in 6xSSC (SSC, 0.15m-sodium chloride-0.015m-sodium citrate) at 66 degrees C was compared with hybridization in formamide-6xSSC (1:1, v/v) at 35 degrees C. As expected, the RNA hybridization potential was labile in the former system and stable in the latter. DNA retention by filters was poor in the formamide system, but could be improved. Several other properties of the hybridization reaction were explored and it was concluded that the formamide system is generally superior.
| S-EPMC1178082 | biostudies-other
Project description:ObjectivePreservation of biological materials at subzero Centigrade temperatures, cryopreservation, is important for the field of tissue engineering and organ transplantation. Our group is studying the use of isochoric (constant volume) systems of aqueous solution for cryopreservation. Previous studies measured the pressure-temperature relations in aqueous isochoric systems in the temperature range from 0°C to - 20°C. The goal of this study is to expand the pressure-temperature measurement beyond the range reported in previous publications.Materials and methodsTo expand the pressure-temperature measurements beyond the previous range, we have developed a new isochoric device capable of withstanding liquid nitrogen temperatures and pressures of up to 413 MPa. The device is instrumented with a pressure transducer than can monitor and record the pressures in the isochoric chamber in real time. Measurements were made in a temperature range from - 5°C to liquid nitrogen temperatures for various solutions of pure water and Me2SO (a chemical additive used for protection of biological materials in a frozen state and for vitrification (glass formation) of biological matter). Undissolved gaseous are is carefully removed from the system.ResultsTemperature-pressure data from - 5°C to liquid nitrogen temperature for pure water and other solutions are presented in this study. Following are examples of some, temperature-pressure values, that were measured in an isochoric system containing pure water: (- 20°C, 187 MPa); (-25°C, 216 MPa); (- 30°C, 242.3 MPa); (-180°C, 124 MPa). The data is consistent with the literature, which reports that the pressure and temperature at the triple point, between ice I, ice III and water is, - 21.993°C and 209.9 MPa, respectively. It was surprising to find that the pressure in the isochoric system increases at temperatures below the triple point and remains high to liquid nitrogen temperatures. Measurements of pressure-temperature relations in solutions of pure water and Me2SO in different concentrations show that, for concentrations in which vitrification is predicted, no increase in pressure was measured during rapid cooling to liquid nitrogen temperatures. However, ice formation either during cooling or warming to and from liquid nitrogen temperatures produced an increase in pressure.ConclusionsThe data obtained in this study can be used to aid in the design of isochoric cryopreservation protocols. The results suggest that the pressure measurement is important in the design of "constant volume" systems and can provide a simple means to gain information on the occurrence of vitrification and devitrification during cryopreservation processes of aqueous solutions in an isochoric system.
| S-EPMC5560655 | biostudies-literature
Project description:Whether screening small mammal serum during antibody production or attempting to preserve a stock of precious antibody, this protocol's western blotting method using aliquots containing nanoliter volumes of antibody will benefit researchers. Time-tested western blotting workflows allowing separation and analysis of proteins are routinely utilized in clinical and laboratory settings. The necessity for relatively large quantities of antibody is a major limitation to this universal tool. This article provides a step-by-step protocol for detecting proteins of interest with solutions containing nanoliter volumes of antibody without altering the preceding gel electrophoresis and transfer methods. Important considerations, frequently encountered problems, and means of optimizing reproducibility are discussed. Complementary diagrams, images, and videos are provided. The protocol is demonstrated using 0.3 nanoliters of anti-serum to detect fibronectin in a human foreskin fibroblast cell line. Finally, two support protocols detailing methods of extracting proteins from cultured cells are reported. Published 2019. This article is a US Government work and is in the public domain in the USA.
| S-EPMC6727981 | biostudies-literature
Project description:This study presents the theory for liquid-liquid phase separation for systems of molecules modeling monoclonal antibodies. Individual molecule is depicted as an assembly of seven hard spheres, organized to mimic the Y-shaped antibody. We consider the antibody-antibody interactions either through Fab, Fab' (two Fab fragments may be different), or Fc domain. Interaction between these three domains of the molecule (hereafter denoted as A, B, and C, respectively) is modeled by a short-range square-well attraction. To obtain numerical results for the model under study, we adapt Wertheim's thermodynamic perturbation theory. We use this model to calculate the liquid-liquid phase separation curve and the second virial coefficient B2. Various interaction scenarios are examined to see how the strength of the site-site interactions and their range shape the coexistence curve. In the asymmetric case, where an attraction between two sites is favored and the interaction energies for the other sites kept constant, critical temperature first increases and than strongly decreases. Some more microscopic information, for example, the probability for the particular two sites to be connected, has been calculated. Analysis of the experimental liquid-liquid phase diagrams, obtained from literature, is presented. In addition, we calculate the second virial coefficient under conditions leading to the liquid-liquid phase separation and present this quantity on the graph B2 versus protein concentration.
| S-EPMC5980754 | biostudies-literature
Project description:G protein-coupled receptors (GPCRs) bind a broad array of extracellular molecules and transmit intracellular signals that initiate physiological responses. The signal transduction functions of GPCRs are inherently related to their structural plasticity, which can be experimentally observed by spectroscopic techniques. Nuclear magnetic resonance (NMR) spectroscopy in particular is an especially advantageous method to study the dynamic behavior of GPCRs. The success of NMR studies critically relies on the production of functional GPCRs containing stable-isotope labeled probes, which remains a challenging endeavor for most human GPCRs. We report a protocol for the production of the human histamine H1 receptor (H1R) in the methylotrophic yeast Pichia pastoris for NMR experiments. Systematic evaluation of multiple expression parameters resulted in a ten-fold increase in the yield of expressed H1R over initial efforts in defined media. The expressed receptor could be purified to homogeneity and was found to respond to the addition of known H1R ligands. Two-dimensional transverse relaxation-optimized spectroscopy (TROSY) NMR spectra of stable-isotope labeled H1R show well-dispersed and resolved signals consistent with a properly folded protein, and 19F-NMR data register a response of the protein to differences in efficacies of bound ligands.
| S-EPMC8146376 | biostudies-literature
Project description:Aqueous two-phase system (ATPS) formation is the macroscopic completion of liquid-liquid phase separation (LLPS), a process by which aqueous solutions demix into 2 distinct phases. We report the temperature-dependent kinetics of ATPS formation for solutions containing a monoclonal antibody and polyethylene glycol. Measurements are made by capturing dark-field images of protein-rich droplet suspensions as a function of time along a linear temperature gradient. The rate constants for ATPS formation fall into 3 kinetically distinct categories that are directly visualized along the temperature gradient. In the metastable region, just below the phase separation temperature, T ph , ATPS formation is slow and has a large negative apparent activation energy. By contrast, ATPS formation proceeds more rapidly in the spinodal region, below the metastable temperature, T meta , and a small positive apparent activation energy is observed. These region-specific apparent activation energies suggest that ATPS formation involves 2 steps with opposite temperature dependencies. Droplet growth is the first step, which accelerates with decreasing temperature as the solution becomes increasingly supersaturated. The second step, however, involves droplet coalescence and is proportional to temperature. It becomes the rate-limiting step in the spinodal region. At even colder temperatures, below a gelation temperature, T gel , the proteins assemble into a kinetically trapped gel state that arrests ATPS formation. The kinetics of ATPS formation near T gel is associated with a remarkably fragile solid-like gel structure, which can form below either the metastable or the spinodal region of the phase diagram.
| S-EPMC6690023 | biostudies-literature