Physicochemical Characteristics of Interaction of Saponins from Holothurians (Sea Cucumbers) with Cell Membranes

In most cases, a herbicide must traverse the cell wall, the plasma membrane, and organellar membranes of a plant cell to reach its site of action where accumulation causes phytotoxicity. The physicochemical characteristics of the herbicide molecule including lipophilicity and acidity, the plant cell membranes, and the electrochemical potential in the plant cell control herbicide absorption and accumulation. Most herbicides move across plant membranes via nonfacilitated diffusion because the membrane's lipid bilayer is permeable to neutral, lipophilic xenobiotics. Passive absorption of lipophilic, ionic herbicides or weak acids can be mediated by an ion-trapping mechanism where the less lipophilic, anionic form accumulates in alkaline compartments of the plant cell. A model that includes the pH and electrical gradients across plant cell membranes better predicts accumulation concentrations in plant cells of weak acid herbicides compared to a model that uses pH only. Herbicides also may accumulate in plant cells by conversion to nonphytotoxic metabolites, binding to cellular constituents, or partitioning into lipids. Evidence exists for herbicide transport across cell membranes via carrier-mediated processes where herbicide accumulation is energy dependent; absorption is saturable and slowed by metabolic inhibitors and compounds of similar structure.

Download Full-text

Comparison of Physicochemical Characteristics and Anticoagulant Activities of Polysaccharides from Three Sea Cucumbers

Marine Drugs ◽

10.3390/md11020399 ◽

2013 ◽

Vol 11 (12) ◽

pp. 399-417 ◽

Cited By ~ 89

Author(s):

Lan Luo ◽

Mingyi Wu ◽

Li Xu ◽

Wu Lian ◽

Jingying Xiang ◽

...

Keyword(s):

Physicochemical Characteristics ◽

Sea Cucumbers

Download Full-text

The Physicochemical Characteristics of Serum Albumin and Erythrocyte Cell Membranes under Normal and Heart Failure Symptom Conditions

BIOPHYSICS ◽

10.1134/s0006350919050051 ◽

2019 ◽

Vol 64 (5) ◽

pp. 721-728

Author(s):

D. I. Grachev ◽

A. L. Dudylina ◽

V. N. Titov ◽

E. K. Ruuge

Keyword(s):

Heart Failure ◽

Serum Albumin ◽

Cell Membranes ◽

Physicochemical Characteristics ◽

Heart Failure Symptom

Download Full-text

Physicochemical Characteristics and Anticoagulant Activities of the Polysaccharides from Sea Cucumber Pattalus mollis

Marine Drugs ◽

10.3390/md17040198 ◽

2019 ◽

Vol 17 (4) ◽

pp. 198 ◽

Cited By ~ 3

Author(s):

Wenqi Zheng ◽

Lutan Zhou ◽

Lisha Lin ◽

Ying Cai ◽

Huifang Sun ◽

...

Keyword(s):

Molecular Weight ◽

Chemical Structure ◽

Sea Cucumber ◽

Biological Activities ◽

Intrinsic Factor ◽

Physicochemical Characteristics ◽

Molar Ratio ◽

Sulfated Polysaccharides ◽

Sea Cucumbers

Sulfated polysaccharides from sea cucumbers possess distinct chemical structure and various biological activities. Herein, three types of polysaccharides were isolated and purified from Pattalus mollis, and their structures and bioactivities were analyzed. The fucosylated glycosaminoglycan (PmFG) had a CS-like backbone composed of the repeating units of {-4-d-GlcA-β-1,3-d-GalNAc4S6S-β-1-}, and branches of a sulfated α-l-Fuc (including Fuc2S4S, Fuc3S4S and Fuc4S with a molar ratio of 2:2.5:1) linked to O-3 of each d-GlcA. The fucan sulfate (PmFS) had a backbone consisting of a repetitively linked unit {-4-l-Fuc2S-α-1-}, and interestingly, every trisaccharide unit in its backbone was branched with a sulfated α-l-Fuc (Fuc4S or Fuc3S with a molar ratio of 4:1). Apart from the sulfated polysaccharides, two neutral glycans (PmNG-1 & -2) differing in molecular weight were also obtained and their structures were similar to animal glycogen. Anticoagulant assays indicated that PmFG and PmFS possessed strong APTT prolonging and intrinsic factor Xase inhibition activities, and the sulfated α-l-Fuc branches might contribute to the anticoagulant and anti-FXase activities of both PmFG and PmFS.

Download Full-text

Photoreceptor disk membrane substructures by means of the complementary freeze-fracture-replica methods

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081644 ◽

1978 ◽

Vol 36 (2) ◽

pp. 156-157

Author(s):

A. Tonosaki ◽

M. Yamasaki ◽

H. Washioka ◽

J. Mizoguchi

Keyword(s):

Cell Membranes ◽

Freeze Fracture ◽

Purple Membrane ◽

Remarkable Case ◽

Single Face ◽

Disk Membrane ◽

Associated Proteins ◽

Photoreceptor Membranes

A vertebrate disk membrane is composed of 40 % lipids and 60 % proteins. Its fracture faces have been classed into the plasmic (PF) and exoplasmic faces (EF), complementary with each other, like those of most other types of cell membranes. The hypothesis assuming the PF particles as representing membrane-associated proteins has been challenged by serious questions if they in fact emerge from the crystalline formation or decoration effects during freezing and shadowing processes. This problem seems to be yet unanswered, despite the remarkable case of the purple membrane of Halobacterium, partly because most observations have been made on the replicas from a single face of specimen, and partly because, in the case of photoreceptor membranes, the conformation of a rhodopsin and its relatives remains yet uncertain. The former defect seems to be partially fulfilled with complementary replica methods.

Download Full-text

Introduction to Cell Membranes at Molecular Resolution

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100070217 ◽

1978 ◽

Vol 36 (3) ◽

pp. 497-502

Author(s):

R.J. Barrnett

Keyword(s):

Cell Membranes ◽

International Federation ◽

Mountain Range ◽

Cellular Membranes ◽

Short History ◽

Biological Organization ◽

Macromolecular Assemblies ◽

The Past

This subject, is like observing the panorama of a mountain range, magnificent towering peaks, but it doesn't take much duration of observation to recognize that they are still in the process of formation. The mountains consist of approaches, materials and methods and the rocky substance of information has accumulated to such a degree that I find myself concentrating on the foothills in the foreground in order to keep up with the advance; the edifices behind form a wonderous, substantive background. It's a short history for such an accumulation and much of it has been moved by the members of the societies that make up this International Federation. My panel of speakers are here to provide what we hope is an interesting scientific fare, based on the fact that there is a continuum of biological organization from biochemical molecules through macromolecular assemblies and cellular membranes to the cell itself. Indeed, this fact explains the whole range of towering peaks that have emerged progressively during the past 25 years.

Download Full-text

Applications of SEM/EDXA in cement clinker investigation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177489 ◽

1990 ◽

Vol 48 (4) ◽

pp. 870-871

Author(s):

Arezki Tagnit-Hamou ◽

Shondeep L. Sarkar

Keyword(s):

Mineralogical Composition ◽

Physicochemical Characteristics ◽

Cement Clinker ◽

Accurate Information ◽

Phase Identification ◽

History Of ◽

Bulk Chemical ◽

Resolution Imaging ◽

Proven Method ◽

Instantaneous Chemical

All the desired properties of cement primarily depend on the physicochemical characteristics of clinker from which the cement is produced. The mineralogical composition of the clinker forms the most important parameter influencing these properties.Optical microscopy provides reasonably accurate information pertaining to the thermal history of the clinker, while XRDA still remains the proven method of phase identification, and bulk chemical composition of the clinker can be readily obtained from XRFA. Nevertheless, all these microanalytical techniques are somewhat limited in their applications, and SEM/EDXA combination fills this gap uniquely by virtue of its high resolution imaging capability and possibility of instantaneous chemical analysis of individual phases.Inhomogeneities and impurities in the raw meal, influence of kiln conditions such as sintering and cooling rate being directly related to the microstructure can be effectively determined by SEM/EDXA. In addition, several physical characteristics of cement, such as rhcology, grindability and hydraulicity also depend on the clinker microstructure.

Download Full-text

Common modifications of selenocysteine in selenoproteins

Essays in Biochemistry ◽

10.1042/ebc20190051 ◽

2019 ◽

Vol 64 (1) ◽

pp. 45-53 ◽

Cited By ~ 1

Author(s):

Elias S.J. Arnér

Keyword(s):

Amino Acids ◽

Covalent Binding ◽

Physicochemical Characteristics ◽

Redox Active

Abstract Selenocysteine (Sec), the sulfur-to-selenium substituted variant of cysteine (Cys), is the defining entity of selenoproteins. These are naturally expressed in many diverse organisms and constitute a unique class of proteins. As a result of the physicochemical characteristics of selenium when compared with sulfur, Sec is typically more reactive than Cys while participating in similar reactions, and there are also some qualitative differences in the reactivities between the two amino acids. This minireview discusses the types of modifications of Sec in selenoproteins that have thus far been experimentally validated. These modifications include direct covalent binding through the Se atom of Sec to other chalcogen atoms (S, O and Se) as present in redox active molecular motifs, derivatization of Sec via the direct covalent binding to non-chalcogen elements (Ni, Mb, N, Au and C), and the loss of Se from Sec resulting in formation of dehydroalanine. To understand the nature of these Sec modifications is crucial for an understanding of selenoprotein reactivities in biological, physiological and pathophysiological contexts.

Download Full-text