The intrinsic viscosity of mixed protein systems, including studies of plasma and serum

Mega macromolecules as single molecule lubricants for hard and soft surfaces

A longstanding goal in science and engineering is to mimic the size, structure, and functionality present in biology with synthetic analogs. Today, synthetic globular polymers of several million molecular weight are unknown, and, yet, these structures are expected to exhibit unanticipated properties due to their size, compactness, and low inter-chain interactions. Here we report the gram-scale synthesis of dendritic polymers, mega hyperbranched polyglycerols (mega HPGs), in million daltons. The mega HPGs are highly water soluble, soft, nanometer-scale single polymer particles that exhibit low intrinsic viscosities. Further, the mega HPGs are lubricants acting as interposed single molecule ball bearings to reduce the coefficient of friction between both hard and soft natural surfaces in a size dependent manner. We attribute this result to their globular and single particle nature together with its exceptional hydration. Collectively, these results set the stage for new opportunities in the design, synthesis, and evaluation of mega polymers.

Synthetic globular polymers of several million molecular weight are expected to exhibit unique properties but are difficult to synthesize. Here the authors synthesize such dendritic polymers that show unique lubrication properties and act as molecular ball bearings due to their 3D compact structure, size, solubility, hydration and low intrinsic viscosities.

Centrifugation affects the purity of liquid biopsy-based tumor biomarkers

Biomarkers in the blood of cancer patients include circulating tumor cells (CTCs), tumor-educated platelets (TEPs), tumor-derived extracellular vesicles (tdEVs), EV-associated miRNA (EV-miRNA), and circulating cell-free DNA (ccfDNA). Because the size and density of biomarkers differ, blood is centrifuged to isolate or concentrate the biomarker of interest. Here, we applied a model to estimate the effect of centrifugation on the purity of a biomarker according to published protocols. The model is based on the Stokes equation and was validated using polystyrene beads in buffer and plasma. Next, the model was applied to predict the biomarker behavior during centrifugation. The result was expressed as the recovery of CTCs, TEPs, tdEVs in three size ranges (1-8, 0.2-1, and 0.05-0.2 μm), EV-miRNA, and ccfDNA. Bead recovery was predicted with errors <18%. Most notable cofounders are the 22% contamination of 1-8 μm tdEVs for TEPs and the 8-82% contamination of <1 μm tdEVs for ccfDNA. A Stokes model can predict biomarker behavior in blood. None of the evaluated protocols produces a pure biomarker. Thus, care should be taken in the interpretation of obtained results, as, for example, results from TEPs may originate from co-isolated large tdEVs and ccfDNA may originate from DNA enclosed in <1 μm tdEVs. © 2018 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

Factors affecting the viscosity in high concentration solutions of different monoclonal antibodies

The viscosity profiles of four different IgG(1) molecules were studied as a function of concentration at pH 6.0. At high concentrations, MAb-H and -A showed significantly higher viscosities as compared to MAb-G and -E. Zeta Potential (ξ) measurements showed that all the IgG(1) molecules carried a net positive charge at this pH. MAb-G showed the highest positive zeta potential followed by MAb-E, -H, and -A. A consistent interpretation of the impact of net charge on viscosity for these MAbs is not possible, suggesting that electroviscous effects cannot explain the differences in viscosity. Values of k(D) (dynamic light scattering) indicated that the intermolecular interactions were repulsive for MAb-E and -G; and attractive for MAb-H and -A. Solution storage modulus (G') in high concentration solutions was consistent with attractive intermolecular interactions for MAb-H and -A, and repulsive interactions for MAb-G and -E. Effect of salt addition on solution G' and k(D) indicated that the interactions were primarily electrostatic in nature. The concentration dependent viscosity data were analyzed using a modified Ross and Minton equation. The analysis explicitly differentiates between the effect of molecular shape, size, self-crowding, and electrostatic intermolecular interactions in governing high concentration viscosity behavior.

Intrinsic viscosity of bovine serum albumin conformers

Intrinsic viscosity of bovine serum albumin (BSA) at different pH values (2.7, 4.3, 7.4, 8 and 10) has been determined, as well as the Mark-Houwink constant and expansion factor. The traditional technique for data analysis using extrapolation to obtain intrinsic viscosity values shows an unusual behavior regarding concentration that can be observed in the values obtained for Huggins' and Kraemer's constants.

Effects of posture on plasma and serum viscosity

This study demonstrates the importance of defining normal reference population ranges for P- and S-viscosity with respect to posture. The normal ranges determined for P-viscosity are not acceptable as a reference range for a hospitalized population that is predominantly in a supine position. Mean percentage changes of P- and S-viscosity in the recumbent posture as compared to the same population in the upright posture were 7.51 and 5.88, respectively.

Disturbance of serum viscosity in diabetes mellitus

The serum viscosity of diabetic patients has been found to be increased. The elevation averaged 8% above healthy subjects and 6% above nondiabetic patients. The serum viscosity elevation was greater when diabetic sequelae associated with microangiopathy were present. No relation of serum viscosity to age, sex, obesity, duration of disease, or type of treatment was demonstrated. Serum total protein and glucose levels were found to be correlated with serum viscosity, and increases in their serum concentrations were observed in diabetes. Analysis demonstrated that their elevation did not explain either the viscosity increase or the difference in viscosity between diabetics with and without sequelae.Intrinsic viscosity, abbreviated [eta], is a concentration-independent solute property related to molecular shape. [eta] was found to be 7% higher in diabetic than in normal serum. The [eta] difference accounted for at least half of the serum viscosity elevation. The rest of the increase was due to increased serum protein level and increased nonprotein solids, presumably glucose and lipid. Associated with increased [eta] was a decline in albumin: globulin ratio and elevation of the acute phase reactant proteins, alpha(1)-acid glycoprotein, alpha(1)-antitrypsin, haptoglobin, and ceruloplasmin. Studies comparing diabetic and normal serum fractionated by using 21.5% sodium sulfate showed that changes in [eta] were attributable to changes in serum protein composition rather than an inherent qualitative disturbance of protein present in one of the fractions. Since serum viscosity is elevated in early diabetes, it may be a part of the metabolic disturbance of diabetes and could play a role in the development of diabetic microangiopathy.

Sonic Energy Effects in Bovine Serum Albumin Solutions

Bovine serum solutions exposed to high-frequency sound were examined by ultracentrifugal, electrophoretic, viscometric, conductivity, light scattering, and optical rotatory dispersion procedures. Parameters determined with treated material were the same as those determined with untreated albumin solutions except for slight differences in rotation, the dispersion constant, and in weight-average molecular weight.

Fluorescein-conjugated bovine albumin; physical and biological properties

Fluorescein-bovine albumin conjugates have been prepared and found not to differ appreciably in size, shape, and homogeneity from the precursor, bovine serum albumin. Fluorescein has also been conjugated to rat plasma proteins. Their disappearance rates from the circulation of rats correspond with those obtained from the use of isotope labeling. Their sites of localization in rat tissues were shown to be in the cytoplasm but not in the nuclei of Kupffer cells, fixed macrophages, granulocytes, and proximal renal tubules. Adsorption to endothelium was a characteristic finding. Extracellular localizations were predominantly in the lumina of blood vessels and proximal renal tubules (but never in the lumina of collecting tubules), and the interstitial fluid of skeletal and cardiac muscle (but not that of glandular organs such as the adrenals, liver, and spleen). BAC absorption from the skin of rabbits requires days whereas sodium fluorescein absorption is measured in hours, attesting to the persistence of the colloidal state of BAC in vivo. Fluorescein conjugates have been used to visualize the transcapillary passage of circulating proteins in the mesenteric circulation of frogs and rats by direct microscopic observation and found to diffuse slowly in the manner predicted for plasma proteins. The normal cutaneous vessels of the rat are impermeable in the gross to the labeled proteins; second degree burn promptly increases the permeability of these vessels rendering the presence of the label detectable in the gross in the skin. The process of labeling does not render guinea pig albumin antigenic, although slight antigenicity results from labeling whole plasma protein. It is believed that sufficient biological evidence is presented to support the conclusion that fluorescein-conjugated plasma proteins, particularly albumin, behave in vivo like their native precursors.