scholarly journals Galloylglucoses of low molecular weight as mordant in electron microscopy. I. Procedure, and evidence for mordanting effect.

1976 ◽  
Vol 70 (3) ◽  
pp. 608-621 ◽  
Author(s):  
N Simionescu ◽  
M Simionescu
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Tannic Acid ◽  
Sodium Borohydride ◽  
Low Molecular Weight ◽  
High Contrast ◽  
Experimental Conditions ◽  
Complex Effect ◽  
Tissue Contrast ◽  
Tissue Specimens

Gallotannin, consisting mainly of low molecular weight esters such as penta- and hexagalloylglucoses (commercially available as tannic acid produced from Turkish nutgall), can be used for increasing and diversifying tissue contrast in electron microscopy. When applied on tissue specimens previously fixed by conventional methods (aldehydes and OsO4), the low molecular weight galloylglucoses (LMGG) penetrate satisfactorily the cells and induce general high contrast with fine delineation of extra- and intracellular structures, especially membranes. In some features, additional details of their intimate configuration are revealed. Various experimental conditions tested indicate that the LMGG display a complex effect on fixed tissues: they act primarily as a mordant between osmium-treated structures and lead, and concomitantly stabilize some tissue components against extraction incurred during dehydration and subsequent processing. Experiments with aldehyde blocking reagents (sodium borohydride and glycine) suggested that the LMGG mordanting effect is not dependent on residual aldehydes groups in tissues.

scholarly journals Structural determinants in a library of low molecular weight gelators

Soft Matter ◽  
2015 ◽  
Vol 11 (6) ◽  
pp. 1174-1181 ◽  
Author(s):  
Kyle L. Morris ◽  
Lin Chen ◽  
Alison Rodger ◽  
Dave J. Adams ◽  
Louise C. Serpell
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Circular Dichroism ◽  
Low Molecular Weight ◽  
Combined Approach ◽  
Structural Determinants ◽  
X Ray ◽  
Fibre Diffraction ◽  
Low Molecular Weight Gelators ◽  
Circular Dichroïsm

The structures of hydrogels formed by naphthalene dipeptide library were explored using a combined approach of electron microscopy, X-ray fibre diffraction and circular dichroism.

scholarly journals Characterization of the structure and composition of gecko adhesive setae

2005 ◽  
Vol 3 (8) ◽  
pp. 441-451 ◽  
Author(s):  
N.W Rizzo ◽  
K.H Gardner ◽  
D.J Walls ◽  
N.M Keiper-Hrynko ◽  
T.S Ganzke ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Electrophoretic Analysis ◽  
Low Molecular Weight ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pattern Characteristic ◽  
Additional Protein ◽  
Adhesive Materials

The ability of certain reptiles to adhere to vertical (and hang from horizontal) surfaces has been attributed to the presence of specialized adhesive setae on their feet. Structural and compositional studies of such adhesive setae will contribute significantly towards the design of biomimetic fibrillar adhesive materials. The results of electron microscopy analyses of the structure of such setae are presented, indicating their formation from aggregates of proteinaceous fibrils held together by a matrix and potentially surrounded by a limiting proteinaceous sheath. Microbeam X-ray diffraction analysis has shown conclusively that the only ordered protein constituent in these structures exhibits a diffraction pattern characteristic of β-keratin. Raman microscopy of individual setae, however, clearly shows the presence of additional protein constituents, some of which may be identified as α-keratins. Electrophoretic analysis of solubilized setal proteins supports these conclusions, indicating the presence of a group of low-molecular-weight β-keratins (14–20 kDa), together with α-keratins, and this interpretation is supported by immunological analyses.

Immunolocalization and characterization of the low molecular weight antigen (4–5 kDa) ofToxoplasma gondiithat elicits an early IgM response upon primary infection

Parasitology ◽  
1994 ◽  
Vol 108 (2) ◽  
pp. 139-145 ◽  
Author(s):  
S. Tomavo ◽  
G. Couvreur ◽  
M. A. Leriche ◽  
A. Sadak ◽  
A. Achbarou ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Monoclonal Antibodies ◽  
Primary Infection ◽  
Low Molecular Weight ◽  
Immuno Electron Microscopy ◽  
Surface Localization

SUMMARYA striking feature of toxoplasmic seroconversion is the prominent and early IgM response to a low molecular weight antigen of 4–5 kDa. Two different monoclonal antibodies directed against the 4–5 kDa antigen have been generated and used to characterize this molecule. Using these monoclonal antibodies, we could demonstrate the surface localization of the lowMrantigen by immunofluorescence and immuno-electron microscopy assays. By immunoblotting, we observed that one of the monoclonal antibodies was unable to recognize the 4–5 kDa antigen in tachyzoites propagated in cell culture, indicating an epitope variability betweenToxoplasma gondiitachyzoites grownin vivoandin vitro. We discuss the implications of this latter finding in the design of diagnostic reagents.

Relationship of Oxygen to the Activity of GR-S Reclaiming Agents

1955 ◽  
Vol 28 (1) ◽  
pp. 308-321
Author(s):  
R. B. Bennett ◽  
G. E. P. Smith
Keyword(s):  
Molecular Weight ◽  
Oxygen Content ◽  
Low Molecular Weight ◽  
Constant Amount ◽  
Experimental Conditions ◽  
Physical Conditions ◽  
Subsequent Exposure ◽  
Relationship Of

Abstract 1. An alkylphenol sulfide reclaiming agent was found to have little activity in the absence of oxygen ; conversely oxygen produced little activity without the reclaiming agent. Together, the oxygen and reclaiming agent showed exceptional activity in attacking a sulfur-cured GR-S gum vulcanizate to produce soluble, low molecular-weight fragments under relatively mild experimental conditions. 2. The solubilizing effects of oxygen with reclaiming oils and the alkylphenol sulfide reclaiming agent were produced without significant increase of the amount of combined oxygen in the acetone or chloroform insoluble portions of the vulcanizate. Large increases of oxygen content were produced quickly by subsequent exposure of the treated and extracted samples to an atmosphere of oxygen. 3. No significant quantity of combined sulfur was removed under experimental conditions involving an excess of liquid reclaiming oils and agents. However, a significant, constant amount of sulfur was removed under conditions in which only small amounts of the reclaiming oils and agents were carried on the surface of the ground vulcanizates. This loss of sulfur was independent of both oxygen and of reclaiming aid and appeared to depend solely on the type of stock and on the physical conditions employed.

scholarly journals Ultra-Low Molecular Weight Photoswitchable Hydrogelators

2020 ◽  
Author(s):  
Fayaz Larik ◽  
Lucy Fillbrook ◽  
Sandra Nurttila ◽  
Adam D Martin ◽  
Rhiannon P. Kuchel ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Transmission Electron Microscopy ◽  
Low Molecular Weight ◽  
X Ray ◽  
Cryogenic Transmission Electron Microscopy ◽  
Hydrogen Bonding Interactions ◽  
Transmission Electron ◽  
Order Of Magnitude ◽  
Rhodamine B Dye

Photoswitchable arylazopyrozoles 2 and 3 form hydrogels at a concentration of 1.2% (w/v). With a molecular weight of 258.11 g/mol, these are the lowest known molecular weight hydrogelators that respond reversibly to light. Single-crystal X-ray structures show anisotropic aggregation of 2 and 3 is driven by in-plane hydrogen bonding interactions and 𝝅 - 𝝅 stacking. Photoswitching of 2 and 3 from the E- to the Z-form by 365 nm light results in a macrocopic gel→sol transition; nearly an order of magnitude reduction in the measured elastic and loss moduli. Cryogenic transmission electron microscopy suggests that the 29±7 nm wide sheets in the E-2 gel state narrow to 13±2 nm upon photoswitching to the predominantly Z-2 solution state. In the case of 2, photoswitching is reversible through cycles of 365 nm and 520 nm excitation with little fatigue. The release of a Rhodamine B dye encapsulated in gels formed from 2 and 3 can be accelerated more than 20-fold upon photoswitching with 365 nm light, demonstrating these materials are suitable for light-controlled cargo release.

Ultra-Low Molecular Weight Photoswitchable Hydrogelators

2020 ◽  
Author(s):  
Fayaz Larik ◽  
Lucy Fillbrook ◽  
Sandra Nurttila ◽  
Adam D Martin ◽  
Rhiannon P. Kuchel ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Transmission Electron Microscopy ◽  
Low Molecular Weight ◽  
X Ray ◽  
Cryogenic Transmission Electron Microscopy ◽  
Hydrogen Bonding Interactions ◽  
Transmission Electron ◽  
Order Of Magnitude ◽  
Rhodamine B Dye

Photoswitchable arylazopyrozoles 2 and 3 form hydrogels at a concentration of 1.2% (w/v). With a molecular weight of 258.11 g/mol, these are the lowest known molecular weight hydrogelators that respond reversibly to light. Single-crystal X-ray structures show anisotropic aggregation of 2 and 3 is driven by in-plane hydrogen bonding interactions and 𝝅 - 𝝅 stacking. Photoswitching of 2 and 3 from the E- to the Z-form by 365 nm light results in a macrocopic gel→sol transition; nearly an order of magnitude reduction in the measured elastic and loss moduli. Cryogenic transmission electron microscopy suggests that the 29±7 nm wide sheets in the E-2 gel state narrow to 13±2 nm upon photoswitching to the predominantly Z-2 solution state. In the case of 2, photoswitching is reversible through cycles of 365 nm and 520 nm excitation with little fatigue. The release of a Rhodamine B dye encapsulated in gels formed from 2 and 3 can be accelerated more than 20-fold upon photoswitching with 365 nm light, demonstrating these materials are suitable for light-controlled cargo release.

Dermatan Sulfate Is a More Potent Inhibitor of Clot-bound Thrombin than Unfractionated and Low Molecular Weight Heparins

1994 ◽  
Vol 71 (05) ◽  
pp. 576-580 ◽  
Author(s):  
P Bendayan ◽  
H Boccalon ◽  
D Dupouy ◽  
B Boneu
Keyword(s):  
Molecular Weight ◽  
Dermatan Sulfate ◽  
Potent Inhibitor ◽  
Final Concentration ◽  
Coagulation Cascade ◽  
Low Molecular Weight ◽  
Dependent Manner ◽  
Low Molecular Weight Heparins ◽  
Experimental Conditions

SummaryClot-bound thrombin proteolyses fibrinogen and amplifies the coagulation cascade at its close vicinity, thereby ensuring the growth of fibrin-rich thrombus. The present study compares the ability of various glycosaminoglycans (GAGs) to inhibit these 2 properties. Unfractionated heparin (UH), 3 low molecular weight heparins (LMWHs) with increasing antifactor Xa/antifactor Ha ratio, the synthetic pentasaccharide (PS), devoid of antifactor Ha activity, and dermatan sulfate (DS), a catalyst of thrombin inhibition by heparin cofactor II, were selected on the basis of their different properties. Proteolysis of fibrinogen by clot-bound thrombin was evaluated by measuring fibrinopeptide A (FPA) generation after an incubation of standardized washed clots in plasma for 120 min in absence or in presence of increasing concentrations of heparins or of DS. The results were compared to those obtained when free a-thrombin (0.4 nM) was added to plasma in the same experimental conditions. On the basis of equivalent antithrombin units, UH and LMWHs gave identical results. To inhibit by 70% fibrinogen proteolysis induced by clot-bound thrombin (IC 70), 5- to 9-fold higher concentrations of UH or of LMWHs were required in comparison with those required to inhibit free thrombin. For DS, only a 1.3 times higher concentration was required. PS (final concentration 1 anti Xa U • ml-1) was devoid of any inhibitory effect. The amplification of the coagulation cascade induced by dot-bound thrombin was evaluated by measuring the shortening of whole blood clotting time (WBCT) resulting from the incubation of washed clots in native blood. In absence of GAG, clot-bound thrombin reduced WBCT from 18 ± 2 min to 9 ± 1 min. Each GAG prolonged WBCT in a dose-dependent manner but these prolongations were smaller in presence of washed clots. The most potent agent to suppress the shortening of WBCT was DS. LMWH and UH were less effective and PS (final concentration 1 anti Xa U/ml) was almost ineffective. Therefore, in these in vitro experiments, DS is a more potent inhibitor of clot-bound thrombin than heparin. Whether or not these observations are relevant for the treatment of established deep-vein thrombosis requires comparative clinical studies.

Functional organogels from lipophilic L-glutamide derivative immobilized on cyclotriphosphazene core

2006 ◽  
Vol 21 (5) ◽  
pp. 1274-1278 ◽  
Author(s):  
Tomohiro Shirosaki ◽  
Saleh Chowdhury ◽  
Makoto Takafuji ◽  
Dzhamil Alekperov ◽  
Galina Popova ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Transmission Electron Microscopy ◽  
Transmission Electron Microscopy Observation ◽  
Low Molecular Weight ◽  
Microscopy Observation ◽  
The Core ◽  
Self Assembling ◽  
Transmission Electron ◽  
Gelation Test

A novel cyclotriphosphazene-based low-molecular weight organogelator was prepared by immobilization of six dialkylated L-glutamide derivatives on a cyclotriphosphazene core, and its ability as a self-assembling organogelator was investigated. The organogelator exhibited enhanced gelation ability and chirality, and thixotropic property for self-restoring to a gel state; this was compared to the corresponding L-glutamide-derived organogelator without the core. The gelation test, transmission electron microscopy observation, and circular dichroism (CD) spectral study showed that the gelation and aggregation ability were enhanced by immobilization onto the cyclotriphosphazene core. Gels in chloroform and cyclohexane-ethanol (95:5) mixture showed an unusual thixotropic property.

Effect Of Some Experimental Conditions On The Activity Of A Low Molecular Weight (LMW) Heparin Fraction Compared To A Hight Molecular Weight (HMW) Fraction

1981 ◽  
Author(s):  
M Aiach ◽  
C Nussas ◽  
J Mardiguian
Keyword(s):  
Molecular Weight ◽  
Incubation Time ◽  
Factor Xa ◽  
Low Molecular Weight ◽  
Experimental Conditions ◽  
Assay Procedure ◽  
At Iii ◽  
Parabolic Function ◽  
Heparin Activity ◽  
Antiprotease Activity

In this work, we aimed to demonstrate that different methods can give different results when the same pair of heparin samples are compared, even when specific antiprotease assays are performed. For this purpose, the effect of heparin on factor Xa (Xa) or thrombin (IIa) inhibition by antithrombin III (AT III) was examined in the presence of varying amounts of AT III, during different incubation times.The molecular weight of the two heparins were 5,200 (LMW) and 42,000 (HMW). Solutions containing 2 y.g per ml of heparin and a 1.4 to 15 μM freshly purified human AT III were incubated with either bovine Xa or human Ila. After a 20, 30, 60 or 90 secondes incubation at 30° C, the remaining protease activity was measured by the initial velocity of a chromogenic substrate. The method was entirely automated using a reaction rate analyser and an adapted program.The antiprotease activity of the LMW heparin (related to the HMW heparin activity) varied from 0.23 to 0.89 in the anti Xa system, from 0.30 to 0.77 in the anti Ila system. The ratio of LMW to HMW activity was a parabolic function of either AT III concentration or incubation time. No meaning differences were observed between anti Xa and anti Ila activity when the inhibiting capacity was assayed in the same experimental conditions. These results suggest that the relative activities of HMW and LMW fractions depend upon the assay procedure. AT III concentration as well as incubation time are of particular importance.

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