scholarly journals Effect of physical environment on the conformation of ricin Influence of low pH

1986 ◽  
Vol 240 (1) ◽  
pp. 221-226 ◽  
Author(s):  
J P Frénoy
Keyword(s):  
Physical Environment ◽  
Analytical Ultracentrifugation ◽  
Ricinus Communis ◽  
Binding Capacity ◽  
Equilibrium Dialysis ◽  
Sedimentation Coefficient ◽  
Living Cells ◽  
Low Ph ◽  
Molecular Properties ◽  
Physical Conditions

The molecular properties of ricin (the toxic lectin from Ricinus communis seeds, RCA II or RCA 60) were evaluated by analytical ultracentrifugation, viscosimetry, c.d., fluorescence and equilibrium dialysis. Measurements of sedimentation (S0(20,W) = 4.60 S) and viscosity (eta = 2.96 × 10(-2) dl/g) indicated that, at neutral pH, the ricin molecule is very compact. Various transitions were explored, and a pH-triggered change in the ricin conformation was observed between pH 7 and 4. In this range, the sedimentation coefficient, far-u.v. c.d. and fluorescence altered simultaneously without unfolding. Below pH 7 the change in the ricin conformation was accompanied by a decrease in the affinity of ricin for galactosides, and at pH 4.0 by an alteration in its binding capacity. These effects of low pH are discussed in relation to the physical conditions encountered by ricin molecules during their entry into living cells.

scholarly journals Structure and stability of Ricinus communis haemagglutinin

1986 ◽  
Vol 240 (1) ◽  
pp. 227-231 ◽  
Author(s):  
J P Frénoy ◽  
A T Tran ◽  
R Bourrillon
Keyword(s):  
Light Scattering ◽  
Thermal Denaturation ◽  
Analytical Ultracentrifugation ◽  
Ricinus Communis ◽  
Low Ph ◽  
Molecular Properties ◽  
Native Structure ◽  
Guanidinium Chloride ◽  
Ph Dependent ◽  
Conformation Transition

The molecular properties of the haemagglutinin of Ricinus communis (RCA I or RCA 120) were evaluated by analytical ultracentrifugation, light-scattering, c.d. and fluorescence. The native molecule had a fairly expanded structure (f/f0 = 1.43) and dissociated into two subunits of equal size in 6 M-guanidinium chloride. This native structure was stable in alkali (up to pH 11) and resistant to thermal denaturation at neutrality. A pH-triggered change in the haemagglutinin conformation was observed and characterized by analytical ultracentrifugation, c.d. and fluorescence between pH 7 and 4.5, the range in which its affinity for galactosides decreased [Yamasaki, Absar & Funatsu (1985) Biochim, Biophys. Acta 828, 155-161]. These results are discussed in relation to those reported in the literature for other lectins and more especially ricin, for which a pH-dependent conformation transition has been observed in the same range of low pH.

Larval Behavior and Protective Implications for Sea Scallops and Surf Clams within the Middle Atlantic Bight: Part Two, Variability of Physical Environment and Larval Behaviors

2019 ◽  
Vol 2 (2) ◽  
Keyword(s):  
Physical Environment ◽  
Climate Changes ◽  
Larval Growth ◽  
Growth Patterns ◽  
Larval Behavior ◽  
Larval Release ◽  
Physical Conditions ◽  
Climatic Variations ◽  
Middle Atlantic ◽  
Sea Scallops

Larval growth and settlement rates are important larval behaviors for larval protections. The variability of larval growthsettlement rates and physical conditions for 2006-2012 and in the future with potential climate changes was studied using the coupling ROMS-IMBs, and new temperature and current indexes. Forty-four experimental cases were conducted for larval growth patterns and release mechanisms, showing the spatial, seasonal, annual, and climatic variations of larval growthsettlement rates and physical conditions, demonstrating that the slight different larval temperature-adaption and larval release strategies made difference in larval growth-settlement rates, and displaying that larval growth and settlement rates highly depended upon physical conditions and were vulnerable to climate changes.

YENİDOĞAN YOĞUN BAKIM ÜNİTELERİNDE İŞ KAZALARI RİSKLERİ VE NEDENLERİNE YÖNELİK BİR ARAŞTIRMA

2015 ◽  
Vol 3 (2) ◽  
Author(s):  
Haluk Tanrıverdi ◽  
Orhan Akova ◽  
Nurcan Türkoğlu Latifoğlu
Keyword(s):  
Intensive Care ◽  
Intensive Care Units ◽  
Physical Environment ◽  
Neonatal Intensive Care ◽  
Organizational Factors ◽  
Occupational Accidents ◽  
Neonatal Intensive Care Units ◽  
Work Related ◽  
Physical Conditions ◽  
The Relationship

This study aims to demonstrate the relationship between the qualifications of neonatal intensive care units of hospitals (physical conditions, standard applications, employee qualifications and use of personal protective equipment) and work related causes and risks, employee related causes and risks when occupational accidents occur. Accordingly, a survey was prepared and was made among 105 nurses working in 3 public and 3 private hospital's neonatal intensive care units, in the January of 2010. The survey consists of questions about the qualifications of neonatal intensive care units, work related causes and risks, and employee related causes and risks. From the regression analysis conducted, it has been found that confirmed hypotheses in several studies in the literature were not significant in this study. The sub-dimensions in which relationships has been found show that the improvement of the physical environment in workplace, the improvement of the employee qualifications and standard applications can reduce the rate of occupational accidents. According to the results of this study management should take care of the organizational factors besides to improvement of the physical environment in workplace, the improvement of the employee qualifications and standard applications.

scholarly journals Measurement of length distribution of beta-lactoglobulin fibrils by multiwavelength analytical ultracentrifugation

2020 ◽  
Vol 49 (8) ◽  
pp. 745-760 ◽  
Author(s):  
Maximilian J. Uttinger ◽  
Timon R. Heyn ◽  
Uwe Jandt ◽  
Simon E. Wawra ◽  
Bettina Winzer ◽  
...  
Keyword(s):  
Scaling Laws ◽  
Amyloid Fibrils ◽  
Analytical Ultracentrifugation ◽  
Length Distribution ◽  
Sedimentation Coefficient ◽  
Size Reduction ◽  
Diameter Distribution ◽  
Cylindrical Shape ◽  
Modal Values ◽  
Beta Lactoglobulin

AbstractThe whey protein beta-lactoglobulin is the building block of amyloid fibrils which exhibit a great potential in various applications. These include stabilization of gels or emulsions. During biotechnological processing, high shear forces lead to fragmentation of fibrils and therefore to smaller fibril lengths. To provide insight into such processes, pure straight amyloid fibril dispersions (prepared at pH 2) were produced and sheared using the rotor stator setup of an Ultra Turrax. In the first part of this work, the sedimentation properties of fragmented amyloid fibrils sheared at different stress levels were analyzed with mulitwavelength analytical ultracentrifugation (AUC). Sedimentation data analysis was carried out with the boundary condition that fragmented fibrils were of cylindrical shape, for which frictional properties are known. These results were compared with complementary atomic force microscopy (AFM) measurements. We demonstrate how the sedimentation coefficient distribution from AUC experiments is influenced by the underlying length and diameter distribution of amyloid fibrils.In the second part of this work, we show how to correlate the fibril size reduction kinetics with the applied rotor revolution and the resulting energy density, respectively, using modal values of the sedimentation coefficients obtained from AUC. Remarkably, the determined scaling laws for the size reduction are in agreement with the results for other material systems, such as emulsification processes or the size reduction of graphene oxide sheets.

scholarly journals Sedimentation coefficient distributions of large particles

The Analyst ◽  
2016 ◽  
Vol 141 (14) ◽  
pp. 4400-4409 ◽  
Author(s):  
Peter Schuck
Keyword(s):  
Analytical Ultracentrifugation ◽  
Sedimentation Coefficient ◽  
Mathematical Framework ◽  
Analysis Methods ◽  
Large Particles

A uniform mathematical framework for sedimentation coefficient distributions in analytical ultracentrifugation establishes new relationships and resolves differences in analysis methods.

Effect of anti-thyroxin autoantibodies on radioimmunoassay of free thyroxin in serum.

1982 ◽  
Vol 28 (6) ◽  
pp. 1389-1391 ◽  
Author(s):  
J Konishi ◽  
Y Iida ◽  
T Kousaka ◽  
K Ikekubo ◽  
T Nakagawa ◽  
...  
Keyword(s):  
Elderly Patient ◽  
Association Constant ◽  
Binding Capacity ◽  
Equilibrium Dialysis ◽  
Graves Disease ◽  
The Third ◽  
Commercial Kits

Abstract Serum thyroxin was nearly or completely undetectable by radioimmunoassay in an elderly patient with Graves' disease being treated with methimazole. Abnormal binding of thyroxin to antibodies of the IgG variety was shown, the association constant of the complex being 8.0 x 10(8) L/mol and the binding capacity 6.3 nmol/g of IgG. The effect of the antibody on results of radioimmunoassay of free thyroxin was studied with three commercial kits, two of which (Clinical Assays and Damon Diagnostics) gave essentially the same values as did equilibrium dialysis. The third (Amersham International) gave falsely high results because the 125I-labeled thyroxin derivative used in the kit was bound by the autoantibody.

Improved direct specific determination of serum iron and total iron-binding capacity.

1980 ◽  
Vol 26 (2) ◽  
pp. 327-331 ◽  
Author(s):  
F Ceriotti ◽  
G Ceriotti
Keyword(s):  
Serum Iron ◽  
Binding Capacity ◽  
Low Ph ◽  
Total Iron ◽  
Total Iron Binding Capacity ◽  
Ascorbic Acid Solution ◽  
Ph Values ◽  
Specific Determination ◽  
Iron Binding Capacity

Abstract Serum iron is released from transferrin and reduced at pH 1.7 by treating serum with a 10 g/L ascorbic acid solution in 0.1 mol/L HCl. When ferrozine is added to this reagent, it forms a complex with iron that is as intensely colored as at higher pH values, and under these conditions no turbidity is produced. The second major interference, that from copper, is eliminated by adding 1 g of thiosemicarbazide per liter, which at a low pH forms a stable, uncolored complex with copper without affecting the reaction of ferrozine with iron.

Temperature-dependent binding of cyclosporine to an erythrocyte protein.

1987 ◽  
Vol 33 (4) ◽  
pp. 481-485 ◽  
Author(s):  
R P Agarwal ◽  
G A Threatte ◽  
R A McPherson
Keyword(s):  
Binding Constant ◽  
Binding Capacity ◽  
Equilibrium Dialysis ◽  
Temperature Dependent ◽  
Fixed Amount ◽  
Competitive Binding Assay ◽  
Plot Analysis ◽  
Binding Data ◽  
Saturation Capacity ◽  
Increasing Temperature

Abstract In this competitive binding assay to measure endogenous binding capacity for cyclosporine (CsA) in erythrocyte lysates, a fixed amount of [3H]CsA plus various concentrations of unlabeled CsA is incubated with aliquots of a test hemolysate. Free CsA is then adsorbed onto charcoal and removed by centrifugation; CsA complexed with a cyclosporine-binding protein (CsBP) remains in the supernate. We confirmed the validity of this charcoal-separation mode of binding analysis by comparison with equilibrium dialysis. Scatchard plot analysis of the results at 4 degrees C yielded a straight line with slope corresponding to a binding constant of 1.9 X 10(7) L/mol and a saturation capacity of approximately 4 mumol per liter of packed erythrocytes. Similar analysis of binding data at 24 degrees C and 37 degrees C showed that the binding constant decreased with increasing temperature, but the saturation capacity did not change. CsBP was not membrane bound but appeared to be freely distributed within erythrocytes. 125I-labeled CsA did not complex with the erythrocyte CsBP. Several antibiotics and other drugs did not inhibit binding between CsA and CsBP. These findings may explain the temperature-dependent uptake of CsA by erythrocytes in whole blood and suggest that measurement of CsBP in erythrocytes or lymphocytes may help predict therapeutic response or toxicity after administration of CsA.

scholarly journals Structure, Subunit Topology, and Actin-binding Activity of the Arp2/3 Complex from Acanthamoeba

1997 ◽  
Vol 136 (2) ◽  
pp. 331-343 ◽  
Author(s):  
R. Dyche Mullins ◽  
Walter F. Stafford ◽  
Thomas D. Pollard
Keyword(s):  
Electron Micrographs ◽  
Actin Filaments ◽  
Analytical Ultracentrifugation ◽  
Fluorescent Antibody ◽  
Complex Molecule ◽  
Gel Filtration ◽  
Sedimentation Coefficient ◽  
Leading Edge ◽  
Actin Binding ◽  
Filament Bundles

The Arp2/3 complex, first isolated from Acanthamoeba castellani by affinity chromatography on profilin, consists of seven polypeptides; two actinrelated proteins, Arp2 and Arp3; and five apparently novel proteins, p40, p35, p19, p18, and p14 (Machesky et al., 1994). The complex is homogeneous by hydrodynamic criteria with a Stokes' radius of 5.3 nm by gel filtration, sedimentation coefficient of 8.7 S, and molecular mass of 197 kD by analytical ultracentrifugation. The stoichiometry of the subunits is 1:1:1:1:1:1:1, indicating the purified complex contains one copy each of seven polypeptides. In electron micrographs, the complex has a bilobed or horseshoe shape with outer dimensions of ∼13 × 10 nm, and mathematical models of such a shape and size are consistent with the measured hydrodynamic properties. Chemical cross-linking with a battery of cross-linkers of different spacer arm lengths and chemical reactivities identify the following nearest neighbors within the complex: Arp2 and p40; Arp2 and p35; Arp3 and p35; Arp3 and either p18 or p19; and p19 and p14. By fluorescent antibody staining with anti-p40 and -p35, the complex is concentrated in the cortex of the ameba, especially in linear structures, possibly actin filament bundles, that lie perpendicular to the leading edge. Purified Arp2/3 complex binds actin filaments with a Kd of 2.3 μM and a stoichiometry of approximately one complex molecule per actin monomer. In electron micrographs of negatively stained samples, Arp2/3 complex decorates the sides of actin filaments. EDC/NHS cross-links actin to Arp3, p35, and a low molecular weight subunit, p19, p18, or p14. We propose structural and topological models for the Arp2/3 complex and suggest that affinity for actin filaments accounts for the localization of complex subunits to actinrich regions of Acanthamoeba.

Characterization of Factor VIII Immune Complexes By Analytical Ultracentrifugation

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3787-3787
Author(s):  
Pete Lollar ◽  
Ernest T. Parker ◽  
John F. Healey ◽  
Christopher B. Doering
Keyword(s):  
Immune Response ◽  
Factor Viii ◽  
Immune Complexes ◽  
Hemophilia A ◽  
Analytical Ultracentrifugation ◽  
Conflicts Of Interest ◽  
Sedimentation Coefficient ◽  
Coagulation Factor ◽  
Velocity Sedimentation ◽  
Molar Excess

Abstract Inhibitory polyclonal IgG antibodies (inhibitors) to factor VIII (fVIII) represent the most significant complication in patients with congenital hemophilia A. FVIII also is the most frequently targeted coagulation factor in autoimmunity. Antibodies recognizing epitopes in the fVIII A2 and C2 domains are present in most inhibitor patients. In the current study, we characterized the hydrodynamic properties of fVIII immune complexes formed by murine anti-human anti-A2 and anti-C2 fVIII monoclonal antibodies (MAbs) 4A4 and 3D12. 4A4 is representative of the most frequently identified group of anti-A2 MAbs identified in the murine hemophilia A immune response to human fVIII. 3D12 is a classical anti-C2 MAb that inhibits the binding of fVIII to von Willebrand factor (VWF) and phospholipid membranes. Velocity sedimentation of immune complexes formed by varying ratios of 4A4 and 3D12 with a high-expression fVIII construct designated ET3 was conducted at 55,000g and 20 °C by measuring protein absorbance at 280 nm in a Beckman XL-I analytical ultracentrifuge. Sedimentation coefficient (s20,w) distributions of fVIII, MAbs and immune complexes were determined using SEDFIT. The sedimentation coefficients of fVIII in the absence of MAbs and of the MAbs in the absence of fVIII were 7.7 S and 6.4 S, respectively. Under conditions of excess MAb (equimolar 4A4 and 3D12 each in five-fold molar excess over fVIII), a 10.3 S immune complex was observed, representing singly-ligated MAbs (Figure, red trace). Under conditions of excess fVIII (fVIII in four-fold molar excess over equimolar 4A4 and 3D12), 11.9 S doubly-ligated MAb complexes were observed (Figure, green trace). A mixture containing equimolar fVIII and 4A4/3D12 MAb binding sites produced a dominant 14.0 S species and a minor 18.8 S species, indicative of cross-linked 3D12-fVIII-4A4 immune complexes (Figure, blue trace). Indefinite association or immunoprecipitation was not observed. These results demonstrate that a biclonal, bivalent anti-fVIII antibody population can form higher-order immune complexes. These complexes may be a driving factor in the immune response to fVIII by promoting B cell activation and/or antigen presentation. Additionally, these results indicate that analytical ultracentrifugation is a useful tool to characterize fVIII immune complexes. Figure Figure. Disclosures No relevant conflicts of interest to declare.

Sign in / Sign up

Export Citation Format

Share Document