Small molecules, molecular weight

Radiation Effects. The primary effect of radiation is the degradation of large molecules to small molecules. Molecular weight reduction can be... 

Small molecules (molecular weight < 5000) are separated using columns with the smallest pore sizes (60-100 A). A column containing a... 

The star fruit toxin seems to be a small molecule (molecular weight less than 500), differing from oxalate and common amino acids. If is a potenf neurofoxin able to induce seizures and death. Preliminary assays, in synaptosomes, indicated that star fruit neurotoxin binds to GABA receptors. 

The detection of chemical contaminants is very important to environmental protection and homeland security. Since the relevant chemicals tend to be very small molecules (molecular weight <1,000 Da), ultrasensitive analytical tools are needed to detect them at low concentrations, down to ng/mL or even pg/mL. Optical ring... 

Although many new developments can be expected in the area of new radiopharmaceuticals based on larger substances such as proteins, cells, etc., we will confine the remainder of our discussion to the design of small molecules (molecular weight < 1000) for use as radiopharmaceuticals. In attempting to design radiopharmaceuticals of this type, it is useful to consider the general information which is known about factors which influence the biodistribution of small molecules. 

Transfer (acceptor) RNA is found in the cytoplasm and nuclear juice as fractions of comparatively small molecules (molecular weight about 25,000), heterogeneous in their nucleotide composition. The functions of these ribonucleic acids are concerned with the transfer of activated amino acids to suitably oriented messenger RNA molecules (templates), thereby permitting interaction between amino acids in the specific order in which. they must exist in a given polypeptide chain. This is achieved by having a special... 

Membrane Sep r tion. The separation of components ofhquid milk products can be accompHshed with semipermeable membranes by either ultrafiltration (qv) or hyperfiltration, also called reverse osmosis (qv) (30). With ultrafiltration (UF) the membrane selectively prevents the passage of large molecules such as protein. In reverse osmosis (RO) different small, low molecular weight molecules are separated. Both procedures require that pressure be maintained and that the energy needed is a cost item. The materials from which the membranes are made are similar for both processes and include cellulose acetate, poly(vinyl chloride), poly(vinyHdene diduoride), nylon, and polyamide (see AFembrane technology). Membranes are commonly used for the concentration of whey and milk for cheesemaking (31). For example, membranes with 100 and 200 p.m are used to obtain a 4 1 reduction of skimmed milk. 

Test Species Test Article Route Monkey, Rhesus Small organic molecule, molecular weight less than 350 Intravenous, 100, 30, 10, and 3 ig/kg (or other dose range) Oral, 1,000, 300, 100, and 10 lg/kg (or other dose range)... 

Biomolecules are organic compounds found in biological systems. Many are relatively small, with molecular weights of less than 1000 g/mol. There are four main families of these small molecules—simple sugars, nucleotides, amino acids, and lipids. Many simple biomolecules are used to synthesize larger compounds that have important cellular functions, as shown in Figure 3.9. 

Enzymes are the reaction catalysts of the biological systems. They are protein in nature (With exception of small group of catalytic RNA molecules). Molecular weight ranges from 12000 to over million. They are specific in action e.g. Urease. Their catalytic activity depends upon the integrity of their native protein conformation. If enzyme is denatured or dissociated into subunits catalytically activity is usually lost. The enzymes carry out transformation of molecules and also mediate transformation of energy e.g. PHOTOSYNTHESIS. 

Biofunctional molecules are those compounds that control such characteristics of organisms as differentiation, growth, metamorphosis, homeostasis, aggregation and reproduction. Both small molecules and macromolecules are used as biofunctional molecules. Chemical synthesis of small biofunctional molecules will be the subject of this book, because I have been engaged in the chemical synthesis of small biofunctional molecules (molecular weight less than 1000) for half a century. 

Many of the organic compounds found in cells are relatively small, with molecular weights of less than 1,000 daltons (D). (One dalton, 1 atomic mass unit is equal to Vi2, the mass of one atom of 12C.) Cells contain four families of small molecules amino acids, sugars, fatty acids, and nucleotides (Table 1.2). Members of each group serve several functions. First, they are used in the synthesis of larger molecules, many of which are polymers. For example, proteins, certain carbohydrates, and nucleic acids are polymers composed of amino acids, sugars, and nucleotides, respectively. Fatty acids are components of several types of lipid (water-insoluble) molecules. 

Small linear or cyclic molecules (molecular weight < 200) including many industrial chemicals otherwise relatively featureless... 

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