Topic
Stokes radius
About: Stokes radius is a research topic. Over the lifetime, 540 publications have been published within this topic receiving 21466 citations.
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Papers
TL;DR: It has been shown that fast protein size-exclusion liquid chromatography (FPLC) is an "inert" technique that does not shift the equilibrium between N, MG, and U states and, therefore, can be used for qualitative and quantitative studies of protein denaturation.
Abstract: Fast protein size-exclusion liquid chromatography (SEC-FPLC) was used to study solvent-induced unfolding of six proteins. Two of them (sperm whale myoglobin and hen white lysozyme) denature on the simple N (native) U (completely unfolded) scheme. The other four proteins [bovine and human alpha-lactalbumin, bovine carbonic anhydrase B (BCAB), and beta-lactamase from Staphylococcus aureus] denature through the molten globule (MG) state (i.e., on the N MG U denaturation scheme). We have shown that the permeation properties of the Superose 12 columns are practically independent of temperature, pH, and denaturants in wide concentration intervals. In the case of myoglobin and lysozyme denaturation at 4 degrees C (when the exchange between the native and unfolded states is slower than the characteristic time of chromatography), a bimodal distribution on molecular dimensions in the transition region was observed. This indicates that, under denaturant action, protein molecules can only be in one of the two states with different compactness. In other words, this shows that FPLC is one of the most direct approaches to establish the "all-or-none" mechanism of the equilibrium solvent-induced denaturation of globular proteins. The curves of guanidinium hydrochloride- (GdmHCl) or urea-induced unfolding (N U or MG U transitions) of a protein on a column (monitored either by the relative areas of two peaks or--for fast exchange--by the position of the average peak) coincide with those monitored by far-UV CD in solution. The Stokes radius values obtained with the use of FPLC for the molten globule states of BCAB (1.6 M GdmHCl in 0.1 M sodium phosphate, pH 6.8, and acid form at pH 3.6) and for the human alpha-lactalbumin molten globule (2.0 M GdmHCl in 0.1 M sodium phosphate, pH 6.8) coincide with those known from literature. Thus, it has been shown that fast protein size-exclusion liquid chromatography (FPLC) is an "inert" technique, i.e., it does not shift the equilibrium between N, MG, and U states and, therefore, can be used for qualitative and quantitative studies of protein denaturation.
458 citations
TL;DR: The results argue strongly for the exclusive localization of the receptor to the cell surface by showing that intracellular membranes or particles have no significant and specific insulin-binding activity.
303 citations
TL;DR: It was found that the lower critical solution temperature (LCST) of PNIPAM decreased as urea was added to the solution, and urea actually facilitated the hydrophobic collapse of the macromolecule.
Abstract: The direct binding mechanism for urea-based denaturation of proteins was tested with a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM). Thermodynamic measurements of the polymer's hydrophobic collapse were complemented by Fourier transform infrared (FTIR) spectroscopy, Stokes radius measurements, and methylated urea experiments. It was found that the lower critical solution temperature (LCST) of PNIPAM decreased as urea was added to the solution. Therefore, urea actually facilitated the hydrophobic collapse of the macromolecule. Moreover, these thermodynamic measurements were strongly correlated with amide I band data which indicated that the decrease in the LCST was coupled to the direct hydrogen bonding of urea to the amide moieties of the polymer. In addition, the hydrogen bonding was found to be highly cooperative, which is consistent with a cross-linking (bivalent binding) mechanism. Cross-linking was confirmed by Stokes radius measurements below the polymer's LCST using gel filtration chromatography. Finally, phase transition measurements with methylurea, dimethylurea, and tetramethylurea indicated that these substituted compounds caused the LCST of PNIPAM to rise with increasing methyl group content. No evidence could be found for the direct binding of any of these methylated ureas to the polymer amide moieties by FTIR. These results are inconsistent with a direct hydrogen-bonding mechanism for the urea-induced denaturation of proteins.
292 citations
TL;DR: The dexamethasone receptor complex in rat liver cytosol has a Stokes radius of 61 A and may be converted to smaller complexes with Stokes radii of 36 A and 19 A by proteolytic digestion with trypsin, a-chymotrypsin (that only gives rise to 36-A complex), papain, or an extract of the 1,000 x g pellet of liver homogenate.
266 citations
TL;DR: Various fluorescent molecular probes have been injected into the cytoplasm of nectary trichome cells of Abutilon striatum to ascertain the conductivity of the plasmodesmata, and it is proposed that in Ab utilon the mobility of a probe is determined solely by the effective Stokes radius of the molecule.
Abstract: Various fluorescent molecular probes have been injected into the cytoplasm of nectary trichome cells of Abutilon striatum to ascertain the conductivity of the plasmodesmata. Most of the probes were based on fluorescein conjugated to a range of amino acids and peptides. The probes are not broken down by cytoplasmic enzymes during the period of observation. The results indicate that there are no specific effects of aromatic amino acids, either polar or hydrophobic types, on the conductivity of the Abutilon plasmodesmata, contrary to reports for other plants. The conductivity of the plasmodesmata in the trichomes is slightly greater than for any that have been studied in the tissues of other plants. It is proposed that in Abutilon the mobility of a probe is determined solely by the effective Stokes radius of the molecule, and that the radius of the molecule is governed by the molecular weight and, in particular, by the nature of the side groups in the peptide chain attached to the fluorochrome. Calculations are presented which indicate that channels between material in the plasmodesmatal annulus are the most likely route for the diffusion of the probes, and that the width of individual channels in the annulus is close to 3 nm.
226 citations
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Performance Metrics
| Year | Papers |
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| 2024 | 1 |
| 2023 | 2 |
| 2022 | 2 |
| 2021 | 1 |
| 2020 | 4 |
| 2019 | 5 |