3. The chemical nature of enzymes

2020 ◽  
pp. 27-48
Author(s):  
Paul Engel
Keyword(s):  
Column Chromatography ◽  
Chemical Nature ◽  
Protein Molecule ◽  
Pure Form ◽  
Large Molecules ◽  
Biological Polymers ◽  
End To End

‘The chemical nature of enzymes’ evaluates the chemical nature of enzymes. To discover the chemical nature of enzymes, it was essential to obtain them in a pure form. To this end, the early biochemists devised various procedures, including fractionation and column chromatography. However, purification of enzymes led to controversy, which ultimately revealed that enzymes are proteins. Proteins are biological polymers, that is, they are built of similar units joined end to end to form very large molecules. Chemically, a protein molecule is a linear polypeptide.

scholarly journals THE CHEMICAL NATURE OF KERATOHYALIN GRANULES OF THE EPIDERMIS

1970 ◽  
Vol 47 (3) ◽  
pp. 593-603 ◽  
Author(s):  
A. Gedeon Matoltsy ◽  
Margit N. Matoltsy
Keyword(s):  
Amino Acids ◽  
Electron Microscope ◽  
Citric Acid ◽  
Column Chromatography ◽  
Chemical Nature ◽  
Newborn Rats ◽  
Amorphous Precursor ◽  
Native Form ◽  
Cell Content

Keratohyalin granules were isolated in the native form from the epidermis of newborn rats by the use of citric acid and a detergent. The isolated granules revealed a fine granular substructure in the electron microscope similar to that seen in situ. Analyses of amino acids by automated column-chromatography showed that proline and cystine are present in large proportions whereas histidine is present in a small amount. Accordingly, it was concluded that keratohyalin represents a sulfur-rich amorphous precursor of the horny cell content, rather than a sulfur-poor side product of the keratinization process, or a unique histidine-rich protein as proposed by in situ histochemical and radioautographic studies.

Amino Acids in Developing Tissues of Xenopus laevis

Development ◽  
1956 ◽  
Vol 4 (4) ◽  
pp. 327-346
Author(s):  
E. M. Deuchar
Keyword(s):  
Amino Acids ◽  
Xenopus Laevis ◽  
Chemical Nature ◽  
Radioactive Tracer ◽  
Protein Molecule ◽  
Chick Embryos ◽  
Histological Differentiation ◽  
Tissue Specific ◽  
Tracer Techniques ◽  
Specific Antigens

Information about embryonic amino acids is of interest because of the possible light it throws on the differentiation of embryonic proteins. It is known from immunological work on amphibian and chick embryos (Cooper, 1946; Clayton, 1953; Ebert, 1950, 1952) that tissue-specific antigens are detectable before histological differentiation has taken place (Ten Cate & van Doorenmaalen, 1950). Although the chemical nature of antigenic differences is not yet properly known, recent evidence suggests that they may include differences in the number and arrangement of amino acids in N-terminal residues of the protein molecule (Porter & Sanger, 1948; McFadden & Smith, 1953; Putnam, 1953). For this reason, and on general grounds too, one may expect the formation of antigens in the embryo to be accompanied by altered arrangements of the proteinbound amino acids. Radioactive tracer techniques have made it possible to detect the uptake of amino acids into embryonic proteins (Waddington & Sirlin, 1954; Feldman & Waddington, 1955), but so far this information has not been related to the appearance of individual antigens.

scholarly journals Granadaene: Proposed Structure of the Group B Streptococcus Polyenic Pigment

2006 ◽  
Vol 72 (9) ◽  
pp. 6367-6370 ◽  
Author(s):  
Manuel Rosa-Fraile ◽  
Javier Rodr�guez-Granger ◽  
Ali Haidour-Benamin ◽  
Juan Manuel Cuerva ◽  
Antonio Sampedro
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Column Chromatography ◽  
Elemental Analysis ◽  
Streptococcus Agalactiae ◽  
Chemical Nature ◽  
Group B Streptococcus ◽  
Red Pigment ◽  
Nuclear Magnetic Resonance Spectra ◽  
Group B

ABSTRACT The goal of this work was to determine the chemical nature of the red pigment produced by Streptococcus agalactiae, which has been thought to be a carotene. We extracted the pigment with 0.1 M KOH and purified it by column chromatography on Sephadex LH. Data from elemental analysis and mass and nuclear magnetic resonance spectra lead us to propose the structure to be that of a new ornithine rhamno-polyene with 12 conjugated double bonds, to which we have assigned the trivial name granadaene.

scholarly journals Straightforward chemical desymmetrisation of cis-(±)-4-O-protected-cyclopent-2-enol using resolving agents on column chromatography

2019 ◽  
Author(s):  
Bemba Sidi Mohamed ◽  
Suzanne Peyrottes ◽  
Jean-Pierre Uttaro ◽  
Christophe MATHE
Keyword(s):  
Silica Gel ◽  
Column Chromatography ◽  
Pure Form ◽  
Starting Material ◽  
Racemic Mixture ◽  
Efficient Procedure ◽  
Resolving Agents

A simple and efficient procedure for the separation of cis-(+)- and cis-(−)-4-O-protected-cyclopent-2-enol, from the corresponding racemic mixture as starting material and using resolving agents, is described. The separation of diasteroisomers was accomplished by flash silica gel column chromatography. The enantiomers cis-(+)- and cis-(−)- of 4-O-protected-cyclopent-2-enol were obtained, in enantiomeric pure form, after elimination of the resolving agents.

The low-resolution 3D-structure of porin, a channel-forming protein in E. coliouter membranes

1983 ◽  
Vol 41 ◽  
pp. 440-441
Author(s):  
A. Engel ◽  
D.L. Dorset ◽  
A. Massalski ◽  
J.P. Rosenbusch
Keyword(s):  
Crystal Packing ◽  
3D Structure ◽  
Gram Negative Bacteria ◽  
Protein Ratio ◽  
Crystal Forms ◽  
Large Molecules ◽  
Functional Studies ◽  
Voltage Dependent ◽  
Planar Membranes ◽  
Hexagonal Arrays

Porins represent a group of channel forming proteins that facilitate diffusion of small solutes across the outer membrane of Gram-negative bacteria, while excluding large molecules (>650 Da). Planar membranes reconstituted from purified matrix porin (OmpF protein) trimers and phospholipids have allowed quantitative functional studies of the voltage-dependent channels and revealed concerted activation of triplets. Under the same reconstitution conditions but using high protein concentrations porin aggregated to 2D lattices suitable for electron microscopy and image processing. Depending on the lipid-to- protein ratio three different crystal packing arrangements were observed: a large (a = 93 Å) and a small (a = 79 Å) hexagonal and a rectangular (a = 79 Å b = 139 Å) form with p3 symmetry for the hexagonal arrays. In all crystal forms distinct stain filled triplet indentations could be seen and were found to be morphologically identical within a resolution of (22 Å). It is tempting to correlate stain triplets with triple channels, but the proof of this hypothesis requires an analysis of the structure in 3 dimensions.

Release of Neurosecretion in the Crayfish Sinus Gland

1968 ◽  
Vol 26 ◽  
pp. 150-151
Author(s):  
Richard R. Shivers
Keyword(s):  
Chemical Nature ◽  
Storage Site ◽  
Neurosecretory Granules ◽  
Sinus Gland ◽  
Diameter Class ◽  
Dense Membrane ◽  
Neurohemal Organ ◽  
Dense Vesicles

The sinus gland is a neurohemal organ located in the crayfish eyestalk and represents a storage site for neurohormones prior to their release into the circulation. The sinus gland contains 3 classes of dense, membrane-limited granules: 1) granules measuring less than 1000 Å in diameter, 2) granules measuring 1100-1400 Å in diameter, and 3) granules measuring 1500-2000 Å in diameter. Class 3 granules are the most electron-dense of the granules found in the sinus gland, while class 2 granules are the most abundant. Generally, all granules appear to undergo similar changes during release.Release of neurosecretory granules may be initiated by a preliminary fragmentation of the “parent granule” into smaller, less dense vesicles which measure about 350 Å in diameter (V, Figs. 1-3). A decrease in density of the granules prior to their fragmentation has been observed and may reflect a change in the chemical nature of the granule contents.

Freeze-fracture cytochemistry: A goal set by Russell Steere in 1957

1993 ◽  
Vol 51 ◽  
pp. 60-61
Author(s):  
Nicholas J Severs
Keyword(s):  
Chemical Nature ◽  
Biological Systems ◽  
Freeze Fracture ◽  
Structural Components ◽  
Major Goal ◽  
Membrane Biology ◽  
Routine Application ◽  
The Future ◽  
Freeze Etching

In his pioneering demonstration of the potential of freeze-etching in biological systems, Russell Steere assessed the future promise and limitations of the technique with remarkable foresight. Item 2 in his list of inherent difficulties as they then stood stated “The chemical nature of the objects seen in the replica cannot be determined”. This defined a major goal for practitioners of freeze-fracture which, for more than a decade, seemed unattainable. It was not until the introduction of the label-fracture-etch technique in the early 1970s that the mould was broken, and not until the following decade that the full scope of modern freeze-fracture cytochemistry took shape. The culmination of these developments in the 1990s now equips the researcher with a set of effective techniques for routine application in cell and membrane biology.Freeze-fracture cytochemical techniques are all designed to provide information on the chemical nature of structural components revealed by freeze-fracture, but differ in how this is achieved, in precisely what type of information is obtained, and in which types of specimen can be studied.

Surgical management of extracranial carotid artery aneurysms

VASA ◽  
2016 ◽  
Vol 45 (3) ◽  
pp. 223-228 ◽  
Author(s):  
Jan Paweł Skóra ◽  
Jacek Kurcz ◽  
Krzysztof Korta ◽  
Przemysław Szyber ◽  
Tadeusz Andrzej Dorobisz ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Surgical Management ◽  
Minor Stroke ◽  
Stroke Rate ◽  
Extracranial Carotid Artery ◽  
Long Term Follow Up ◽  
End To End ◽  
Dacron Patch ◽  
Major Stroke

Abstract. Background: We present the methods and results of the surgical management of extracranial carotid artery aneurysms (ECCA). Postoperative complications including early and late neurological events were analysed. Correlation between reconstruction techniques and morphology of ECCA was assessed in this retrospective study. Patients and methods: In total, 32 reconstructions of ECCA were performed in 31 symptomatic patients with a mean age of 59.2 (range 33 - 84) years. The causes of ECCA were divided among atherosclerosis (n = 25; 78.1 %), previous carotid endarterectomy with Dacron patch (n = 4; 12.5 %), iatrogenic injury (n = 2; 6.3 %) and infection (n = 1; 3.1 %). In 23 cases, intervention consisted of carotid bypass. Aneurysmectomy with end-to-end suture was performed in 4 cases. Aneurysmal resection with patching was done in 2 cases and aneurysmorrhaphy without patching in another 2 cases. In 1 case, ligature of the internal carotid artery (ICA) was required. Results: Technical success defined as the preservation of ICA patency was achieved in 31 cases (96.9 %). There was one perioperative death due to major stroke (3.1 %). Two cases of minor stroke occurred in the 30-day observation period (6.3 %). Three patients had a transient hypoglossal nerve palsy that subsided spontaneously (9.4 %). At a mean long-term follow-up of 68 months, there were no major or minor ipsilateral strokes or surgery-related deaths reported. In all 30 surviving patients (96.9 %), long-term clinical outcomes were free from ipsilateral neurological symptoms. Conclusions: Open surgery is a relatively safe method in the therapy of ECCA. Surgical repair of ECCAs can be associated with an acceptable major stroke rate and moderate minor stroke rate. Complication-free long-term outcomes can be achieved in as many as 96.9 % of patients. Aneurysmectomy with end-to-end anastomosis or bypass surgery can be implemented during open repair of ECCA.

Cell parameters refinements showing an influence of the chemical nature of the grain surface on the crystalline characteristics of fine grained powders

1998 ◽  
Vol 08 (PR5) ◽  
pp. Pr5-85-Pr5-89
Author(s):  
P. Sarrazin ◽  
F. Bernard ◽  
G. Calvarin ◽  
J. C. Niepce ◽  
B. Thierry
Keyword(s):  
Chemical Nature ◽  
Cell Parameters ◽  
Fine Grained ◽  
Grain Surface
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