Ice-active substances associated with Antarctic freshwater and terrestrial photosynthetic organisms

2000 ◽  
Vol 12 (4) ◽  
pp. 418-424 ◽  
Author(s):  
James A. Raymond ◽  
Christian H. Fritsen
Keyword(s):  
Molecular Weight ◽  
North America ◽  
Ice Crystals ◽  
Dry Valleys ◽  
Cyanobacterial Mats ◽  
Cold Environments ◽  
Photosynthetic Organisms ◽  
Eukaryotic Algae ◽  
Dialysis Membranes ◽  
Active Substances

Macromolecular substances that cause pitting and other modifications of growing ice crystals were found to be associated with cyanobacterial mats, eukaryotic algae and mosses from Ross Island and the McMurdo Dry Valleys, Antarctica. Ice-pitting activities were largely retained by dialysis membranes with molecular weight cut-offs of up to 300 kDa. Unlike most aqueous solutes, the ice-active molecules were not excluded from the ice phase during freezing. The ice-pitting activities of each of the samples tested was destroyed by exposure to temperatures between 45 and 65°C, suggesting that they have a protein component. Ice-active substances were not found in cyanobacteria or mosses from temperate climates, but ice-activity was found to be associated with mosses from cold habitats in North America. Although the function of the ice-active substances is not known, their apparent confinement to cold environments suggests that they have a cryoprotective role.

scholarly journals Average molecular weight of surfactants in aerosols

2007 ◽  
Vol 7 (5) ◽  
pp. 13805-13838 ◽  
Author(s):  
M. T. Latif ◽  
P. Brimblecombe
Keyword(s):  
Molecular Weight ◽  
Surface Tension ◽  
Atmospheric Aerosols ◽  
Average Molecular Weight ◽  
Molecular Size ◽  
Weight Fraction ◽  
Ozone Exposure ◽  
Before And After ◽  
Fine Mode ◽  
Active Substances

Abstract. Surfactants in atmospheric aerosols determined as methylene blue active substances (MBAS) and ethyl violet active substances (EVAS). The MBAS and EVAS concentrations can be correlated with surface tension as determined by pendant drop analysis. The effect of surface tension was more clearly indicated in fine mode aerosol extracts. The concentration of MBAS and EVAS was determined before and after ultrafiltration analysis using AMICON centrifuge tubes that define a 5000 Da (5 K Da) nominal molecular weight fraction. Overall, MBAS and to a greater extent EVAS predominates in fraction with molecular weight below 5 K Da. In case of aerosols collected in Malaysia the higher molecular fractions tended to be a more predominant. The MBAS and EVAS are correlated with yellow to brown colours in aerosol extracts. Further experiments showed possible sources of surfactants (e.g. petrol soot, diesel soot) in atmospheric aerosols to yield material having molecular size below 5 K Da except for humic acid. The concentration of surfactants from these sources increased after ozone exposure and for humic acids it also general included smaller molecular weight surfactants.

scholarly journals Micellar Carriers Based on Amphiphilic PEG/PCL Graft Copolymers for Delivery of Active Substances

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2876 ◽  
Author(s):  
Justyna Odrobińska ◽  
Dorota Neugebauer
Keyword(s):  
Molecular Weight ◽  
Graft Copolymers ◽  
Drug Loading ◽  
Polymer System ◽  
Amphiphilic Copolymers ◽  
Bioactive Substances ◽  
Click Reactions ◽  
Micellar Systems ◽  
Active Substances

Amphiphilic copolymers of alkyne functionalized 2-hydroxyethyl methacrylate (AlHEMA) and poly(ethylene glycol) methyl ether methacrylate (MPEGMA) with graft or V-shaped graft topologies were synthesized. The functionalization of poly(ε-caprolactone) (PCL) with azide group enabled attachment to P(AlHEMA-co-MPEGMA) copolymers via a “click” alkyne-azide reaction. The introduction of PCL as a second side chain type in addition to PEG resulted in heterografted copolymers with modified properties such as biodegradability. “Click” reactions were carried out with efficiencies between 17–70% or 32–50% (for lower molecular weight PCL, 4000 g/mol, or higher molecular weight PCL, 9000 g/mol, respectively) depending on the PEG grafting density. The graft copolymers were self-assembled into micellar superstructures with the ability to encapsulate active substances, such as vitamin C (VitC), arbutin (ARB) or 4-n-butylresorcinol (4nBRE). Drug loading contents (DLC) were obtained in the range of 5–55% (VitC), 39–91% (ARB) and 42–98% (4nBRE). In vitro studies carried out in a phosphate buffer saline (PBS) solution (at pH 7.4 or 5.5) gave the maximum release levels of active substances after 10–240 min depending on the polymer system. Permeation tests in Franz chambers indicated that the bioactive substances after release by micellar systems penetrated through the artificial skin membrane in small amounts, and a majority of the bioactive substances remained inside the membrane, which is satisfactory for most cosmetic applications.

scholarly journals Callus of American ginseng (Panax quinquefolius) as a source of ginsenosides – medicinal secondary metabolites

2013 ◽  
Vol 50 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Ewa Kochan ◽  
Aleksander Chmiel
Keyword(s):  
North America ◽  
Secondary Metabolites ◽  
Traditional Medicine ◽  
Panax Ginseng ◽  
American Ginseng ◽  
Panax Quinquefolius ◽  
In Vitro Methods ◽  
Derivatives Of ◽  
Active Substances

Abstract:Asian ginseng (Panax ginseng) and American ginseng (P. quinquefolius) are valuable medicinal herbs whose roots have been used for ages in traditional medicine in China and North America as vitalizing and stimulating agents. The roots are obtained mainly from field cultivation, which is a slow (5-7 years long), laborious, and troublesome process; so in vitro methods started to be used to produce ginseng biomass. In our study, non-organogenic callus of P. quinquefolius synthesized the same active substances like field roots, for more than 6 years. The ginsenosides are derivatives of protopanaxadiol (Rb1, Rb2, Rc, Rd) or protopanaxatriol (Rg1, Re). The synthesis of Rg1and Re metabolites is preferred in calli cultured in the dark and with ageing of culture.

Dialysis Membranes Today

2002 ◽  
Vol 25 (5) ◽  
pp. 447-460 ◽  
Author(s):  
S. K. Bowry
Keyword(s):  
Molecular Weight ◽  
Blood Compatibility ◽  
Hydraulic Permeability ◽  
Product Portfolio ◽  
Small Molecular Weight ◽  
Simple Diffusion ◽  
Technical Developments ◽  
Advanced Therapy ◽  
Clinical Benefits ◽  
Dialysis Membranes

In recent years, hemodialytic therapies have evolved from the simple, diffusion-dependent removal of small molecular weight substances from blood to advanced therapy modalities involving the convective removal of larger uremic sloutes. The clinical benefits of removal of substances such as ß2-microglobulin (ß2-m) have been reported by several authors: elimination of large-molecular weight “uremic toxins” is now widely accepted as being beneficial to the overall quality of life of patients. This trend would not have been possible without parallel technical developments, especially that of new membranes having more open pore structures resulting in higher sieving coefficients and increased hydraulic permeability. Not all polymer types are suitable for the manufacture of high-flux membranes required for convective therapies in which large fluid volumes are exchanged. Amongst the more important criteria are: the selected polymer must be able to undergo steam sterilisation, have high endotoxin retention capabilities, be versatile for the fabrication of a range of hydraulic permeabilities and, of course, have high blood compatibility. The aim of this paper is, firstly, to review the major membrane development phases over the last quarter of a century. Secondly, the suitability of current membrane materials to meet the aforementioned requirements will be examined. Thirdly, in view of the recent, rapid proliferation of polysulfone-based membranes, dialysis membranes of the polysulfone ‘family’ are placed under scrutiny; membranes of this class represent a significant portion of the product portfolio of dialyser manufacturers today, yet, few end-users are able to distinguish between the salient features of the respective products because of a combination of confusing membrane nomenclature, classification, tradenames and product claims.

scholarly journals Low-molecular-weight, fatty-acid esters as potential low-temperature drilling fluids for ice coring

2014 ◽  
Vol 55 (68) ◽  
pp. 39-43 ◽  
Author(s):  
Huiwen Xu ◽  
Lili Han ◽  
Pinlu Cao ◽  
Mingyi Guo ◽  
Junjie Han ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Fatty Acid ◽  
Butyl Acetate ◽  
Drilling Fluid ◽  
High Viscosity ◽  
Fatty Acid Esters ◽  
Low Molecular Weight ◽  
Drilling Fluids ◽  
Cold Environments ◽  
Acid Esters

AbstractA challenge for future deep-ice coring in central Antarctica is to identify an appropriate inert drilling fluid with no undesirable physical or chemical characteristics. The drilling fluids currently in use (kerosene-based fluids with density-increasing additives, ethanol and n-butyl acetate) are not intelligent choices for the future from safety, environmental and some technological standpoints. Recently proposed drilling fluids based upon ESTISOL™ have high viscosity at low temperatures, which severely limits their application in cold environments. This paper presents our research into the application of low-molecular-weight, fatty-acid esters (FAEs), substances commonly used in the fragrance and flavoring industries. According to available data, selected FAEs are not hazardous to human health. Considering density requirements alone, ethyl butyrate and n-propyl propionate best meet our present needs. The viscosities of these two chemicals are also the lowest among studied FAEs, not exceeding 4 mPas at temperatures down to −60°C. Both compounds are highly volatile, and insoluble in water. Such properties are attractive, but the applicability of FAEs to deep, cold, ice drilling can be evaluated only after field-based, practical experiments in test boreholes.

scholarly journals Comparative study of technologies for extraction of biologically active substances from the raw material of animal origin

2021 ◽  
Vol 6 (3) ◽  
pp. 226-235
Author(s):  
E. R. Vasilevskaya ◽  
M. A. Aryuzina ◽  
E. S. Vetrova
Keyword(s):  
Molecular Weight ◽  
Trichloroacetic Acid ◽  
Biologically Active Substances ◽  
Biologically Active ◽  
Animal Origin ◽  
Low Molecular Weight ◽  
Acid Extraction ◽  
Trichloroacetic Acid Solution ◽  
Wide Range ◽  
Active Substances

Technologies of isolation and concentration of biologically active substances, developed in the middle of the 20th century, need adjustment and adaptation to modern conditions both to increase the activity of substances and for greater economic efficiency. The aim of the research is the comparison of dynamics of biologically active compounds extraction from porcines pancreas in two methods: the saline method based on 0.9% sodium chloride solution, and the acidic method based on 2.4% trichloroacetic acid solution. Also the purpose of research is to assess the possibilities for further optimization of technologies. The total protein concentration based on the biuret reaction in the samples taken during the extraction, as well as the calculation and analysis of the point degrees and rates of extraction are chosen as the controlled parameters. Local maxima of the protein yields into the extractant media at the 60th, 135th and 255th minute were recorded during saline extraction; and at the 75th and 135th minute during acid extraction. Also the proteomic profile of the extracts was studied. Wide range of compounds with molecular weight of less than 52 kDa was found in extracts based on physiological saline solution, and protein substances of whole presented range of molecular weights in trichloroacetic acid based extracts were considered. The predominance of low molecular weight protein fraction of interest was noted also in this method of extraction in comparison with the other methods of extraction. According to the UniProt database, we assume availability of probable compounds with a molecular weight of less than 30 kDa in the purified acidic extract. The presence of some proteins absent in the final saline extract was noted. The acidic erythrograms showed a weak degrading effect of both types of extracts on the membranes of rat erythrocytes, as well as the cytoprotective effect of acidic ultrafiltrates (less than 3 kDa). The obtained results prove a better efficiency of trichloroacetic acid extraction method used for obtaining a mixture of a wide range of compounds, including biologically active substances of low molecular weight.

scholarly journals RESEARCH OF GLYCEROL-CONTAINING SURFACTANTS IN FOOD AND PROCESSING INDUSTRIES

2020 ◽  
pp. 141-148
Author(s):  
Yurii Polievoda
Keyword(s):  
Molecular Weight ◽  
Molecular Distillation ◽  
Production Method ◽  
Complete Classification ◽  
Dietary Fats ◽  
Side Reactions ◽  
Reaction Products ◽  
Temperature Regimes ◽  
Surface Active ◽  
Active Substances

The article presents information on surfactants. Given their complete classification, methods of obtaining glaringly surface-active substances (surfactants). A list of surfactants concerning natural and synthetic substances is presented. Proven to be the most promising (cheap) production method of surface-active substances is transesterification oils and fats as the most simple in technological implementation. Presents the results of a study of the effect of surfactants on the protective, flavouring and structural properties of foods. Identified a number of features in the character of interaction of components in the system of food and processing industry – surface-active substance. Methods of obtaining distillation emulsifiers of glycerol fatty acids and transesterification of triglycerides with glycerol are investigated. The main physico-mechanical properties of glycerine all grades. There is a need to obtain surfactants synthetically. Analyzed the technology of production of new method ethanols emulsifiers of dietary fats by distillation of low molecular weight acids with ethyl alcohol and subsequent transesterification dietary fat. Describes the technologically-line of obtaining these emulsifiers T – 1 and T – F. Details are given broad temperature regimes of the process. Describes the manufacturing process of the monoglycerides and their derivatives, obtained by separation of the mixture of reaction products of glycerol, unreacted, digald and products of side reactions by centrifugation and molecular distillation. The technological schemes of obtaining all kinds of monoglycerides and the process of molecular distillation as a method of fractional distillation of high molecular weight liquids are considered.

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