ChemInform Abstract: Suzuki Polycondensation: On Catalyst Derived Phosphorus Incorporation and Reproducibility of Molecular Weights.

Electron microscopic methods have been applied increasingly during the past fifteen years, to problems in structural molecular biology. Used in conjunction with physical chemical methods and/or Fourier methods of analysis, they constitute powerful tools for determining sizes, shapes and modes of aggregation of biopolymers with molecular weights greater than 50, 000. However, the application of the e.m. to the determination of very fine structure approaching the limit of instrumental resolving power in biological systems has not been productive, due to various difficulties such as the destructive effects of dehydration, damage to the specimen by the electron beam, and lack of adequate and specific contrast. One of the most satisfactory methods for contrasting individual macromolecules involves the deposition of heavy metal vapor upon the specimen. We have investigated this process, and present here what we believe to be the more important considerations for optimizing it. Results of the application of these methods to several biological systems including muscle proteins, fibrinogen, ribosomes and chromatin will be discussed.

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Characterization of microtubules by dark-field STEM and replication

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010008506x ◽

1991 ◽

Vol 49 ◽

pp. 152-153

Author(s):

S.B. Andrews ◽

R.D. Leapman ◽

P.E. Gallant ◽

T.S. Reese

Keyword(s):

Protein Interactions ◽

Low Dose ◽

Unit Length ◽

Dark Field ◽

Carbon Films ◽

Microtubule Associated Proteins ◽

Molecular Weights ◽

Freeze Dried ◽

Protein Motors ◽

Associated Proteins

As part of a study on protein interactions involved in microtubule (MT)-based transport, we used the VG HB501 field-emission STEM to obtain low-dose dark-field mass maps of isolated, taxol-stabilized MTs and correlated these micrographs with detailed stereo images from replicas of the same MTs. This approach promises to be useful for determining how protein motors interact with MTs. MTs prepared from bovine and squid brain tubulin were purified and free from microtubule-associated proteins (MAPs). These MTs (0.1-1 mg/ml tubulin) were adsorbed to 3-nm evaporated carbon films supported over Formvar nets on 600-m copper grids. Following adsorption, the grids were washed twice in buffer and then in either distilled water or in isotonic or hypotonic ammonium acetate, blotted, and plunge-frozen in ethane/propane cryogen (ca. -185 C). After cryotransfer into the STEM, specimens were freeze-dried and recooled to ca.-160 C for low-dose (<3000 e/nm2) dark-field mapping. The molecular weights per unit length of MT were determined relative to tobacco mosaic virus standards from elastic scattering intensities. Parallel grids were freeze-dried and rotary shadowed with Pt/C at 14°.

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Electron Microscope Study of RNA's of Paramyxoviruses

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100094231 ◽

1972 ◽

Vol 30 ◽

pp. 196-197

Author(s):

Ruchama Baum ◽

J.T. Seto

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Electron Microscope Study ◽

Sendai Virus ◽

Sodium Dodecyl ◽

Rna Molecules ◽

Virus Particles ◽

Molecular Weights ◽

Length Measurements

The ribonucleic acid (RNA) of paramyxoviruses has been characterized by biochemical and physiochemical methods. However, paramyxovirus RNA molecules have not been studied by electron microscopy. The molecular weights of these single-stranded viral RNA molecules are not known as yet. Since electron microscopy has been found to be useful for the characterization of single-stranded RNA, this investigation was initiated to examine the morphology and length measurements of paramyxovirus RNA's.Sendai virus Z strain and Newcastle disease virus (NDV), Milano strain, were used. For these studies it was necessary to develop a method of extracting RNA molecules from purified virus particles. Highly purified Sendai virus was treated with pronase (300 μg/ml) at 37°C for 30 minutes and the RNA extracted by the sodium dodecyl sulfate (SDS)-phenol procedure.

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Nucleic Acid Molecules Prepared by Monolayer Techniques

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100094140 ◽

1972 ◽

Vol 30 ◽

pp. 178-179

Author(s):

Dimitrij Lang

Keyword(s):

Electron Microscopy ◽

Standard Deviation ◽

Nucleic Acid ◽

Cytochrome C ◽

Nucleic Acids ◽

Contour Length ◽

Sample Standard Deviation ◽

Molecular Weights ◽

Length Measurements ◽

Protein Monolayer

The success of the protein monolayer technique for electron microscopy of individual DNA molecules is based on the prevention of aggregation and orientation of the molecules during drying on specimen grids. DNA adsorbs first to a surface-denatured, insoluble cytochrome c monolayer which is then transferred to grids, without major distortion, by touching. Fig. 1 shows three basic procedures which, modified or not, permit the study of various important properties of nucleic acids, either in concert with other methods or exclusively:1) Molecular weights relative to DNA standards as well as number distributions of molecular weights can be obtained from contour length measurements with a sample standard deviation between 1 and 4%.

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Molecular Weights

Scientific American ◽

10.1038/scientificamerican04281888-10271csupp ◽

1888 ◽

Vol 25 (643supp) ◽

pp. 10271-10272

Keyword(s):

Molecular Weights

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Palladium catalyzed cross-coupling reactions of difunctional derivatives Bu3SnArBr. Synthesis of regioregular poly(3-alkylthiophenes) and poly(4-alkyl 2,2'-bithiophenes) with high molecular weights

Journal de Chimie Physique ◽

10.1051/jcp:1998259 ◽

1998 ◽

Vol 95 (6) ◽

pp. 1250-1253 ◽

Cited By ~ 5

Author(s):

J.-P. Lère-Porte ◽

J. J.E. Moreau ◽

C. Torreilles

Keyword(s):

Cross Coupling ◽

Coupling Reactions ◽

Molecular Weights ◽

Cross Coupling Reactions ◽

Regioregular Poly ◽

Palladium Catalyzed

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Investigation by HPLC of the Catabolism of Recombinant Tissue Plasminogen Activator in the Rat

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647645 ◽

1988 ◽

Vol 60 (01) ◽

pp. 107-112 ◽

Cited By ~ 4

Author(s):

Roy Harris ◽

Louis Garcia Frade ◽

Lesley J Creighton ◽

Paul S Gascoine ◽

Maher M Alexandroni ◽

...

Keyword(s):

Molecular Weight ◽

Plasminogen Activator ◽

Tissue Plasminogen Activator ◽

Half Life ◽

Recombinant Tissue Plasminogen Activator ◽

Rat Plasma ◽

High Molecular Weight Complex ◽

Molecular Weights ◽

Major Activity ◽

Tissue Plasminogen

SummaryThe catabolism of recombinant tissue plasminogen activator (rt-PA) was investigated after injection of radiolabelled material into rats. Both Iodogen and Chloramine T iodination procedures yielded similar biological activity loss in the resultant labelled rt-PA and had half lives in the rat circulation of 1 and 3 min respectively. Complex formation of rt-PA was investigated by HPLC gel exclusion (TSK G3000 SW) fractionation of rat plasma samples taken 1-2 min after 125I-rt-PA injection. A series of radiolabelled complexes of varying molecular weights were found. However, 60% of the counts were associated with a single large molecular weight complex (350–500 kDa) which was undetectable by immunologically based assays (ELISA and BIA) and showed only low activity with a functional promoter-type t-PA assay. Two major activity peaks in the HPLC fractions were associated with Tree t-PA and a complex having a molecular weight of ̴ 180 kDa. HPLC fractionation to produce these three peaks at various timed intervals after injection of 125I-rt-PA showed each to have a similar initial rate half life in the rat circulation of 4-5 min. The function of these complexes as yet is unclear but since a high proportion of rt-PA is associated with a high molecular weight complex with a short half life in the rat, we suggest that the formation of this complex may be a mechanism by which t-PA activity is initially regulated and finally cleared from the rat circulation.

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Permeability Enhancing and Chemotactic Activities of Lower Molecular Weight Degradation Products of Human Fibrinogen

Thrombosis and Haemostasis ◽

10.1055/s-0038-1650136 ◽

1981 ◽

Vol 45 (01) ◽

pp. 090-094 ◽

Cited By ~ 52

Author(s):

Katsuo Sueishi ◽

Shigeru Nanno ◽

Kenzo Tanaka

Keyword(s):

Molecular Weight ◽

Degradation Products ◽

Electron Microscopic Observation ◽

Chemotactic Activity ◽

Lower Molecular Weight ◽

Electron Microscopic ◽

Human Fibrinogen ◽

Rabbit Skin ◽

Molecular Weights ◽

Active Fragments

SummaryFibrinogen degradation products were investigated for leukocyte chemotactic activity and for enhancement of vascular permeability. Both activities increased progressively with plasmin digestion of fibrinogen. Active fragments were partially purified from 24 hr-plasmin digests. Molecular weights of the permeability increasing and chemotactic activity fractions were 25,000-15,000 and 25,000 respectively. Both fractions had much higher activities than the fragment X, Y, D or E. Electron microscopic observation of the small blood vessels in rabbit skin correlated increased permeability with the formation of characteristic gaps between adjoining endothelial cells and their contraction.These findings suggest that lower molecular weight degradation products of fibrinogen may be influential in contributing to granulocytic infiltration and enhanced permeability in lesions characterized by deposits of fibrin and/or fibrinogen.

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