Molecular mass definition

Misunderstandings arise when membrane users assume that MWCO means what it seems to say. The definition implies that a 50 kD membrane will separate a 25 kD material from a 75 kD material. The rule of thumb is that the molecular mass must differ by a factor of ten for a good separation. Special techniques are used to permit the separation of proteins with much smaller mass ratio. 

Polymers generally do not have definite molecular masses because there is no fixed point at which the chainlengthening process will cease. There is no fixed molar mass, only an average molar mass. Because there is no one unique compound, there is no one unique melting point, rather a range of melting points. 

Water soluble protein with a relative molecular mass of ca. 32600, which particularly contains copper and zinc bound like chelate (ca. 4 gram atoms) and has superoxide-dismutase-activity. It is isolated from bovine liver or from hemolyzed, plasma free erythrocytes obtained from bovine blood. Purification by manyfold fractionated precipitation and solvolyse methods and definitive separation of the residual foreign proteins by denaturizing heating of the orgotein concentrate in buffer solution to ca. 65-70 C and gel filtration and/or dialysis. 

Now the function displays the number fraction of molecules with a certain molecular mass. Its integral is 1 by definition. Nevertheless, we still call it the number molecular weight distribution because the factor /N (A/) dM is nothing but a constant. 

The obvious definition of the number average, Mn, of the distribution is the position on the M-axis that divides the area under the n (A/)- curve in equal parts (cf. Fig. 1.3). Because of the fact that n M) is normalized to 1, each of the subareas is equal to 0.5. As 50% of all the molecules are shorter than Mn, the other 50% are longer than Mn. Bearing in mind the normalization, the number average molecular mass is... 

A small amount of the substance is accurately weighed, dissolved and made up carefully in a volumetric flask. to a definite volume, e.g. 100 ml. From the known relative molecular mass (RMM) of the compound it is possible to calculate the molar concentration of the solution ... 

Webster s definition for database is a large collection of data in a computer, organized so that it can be expanded, updated, and retrieved rapidly for various uses. An LC/MS database established for drug impurities contains multi-dimensional information such as relative retention times, UV spectra, molecular mass and substructural information. In order for the information to be updated and expanded, the methods used for information collection need to be unified. A generic LC/MS method allows relevant information to be collected in a consistent... 

Note 2 In the literature, the term macrocycle is sometimes used for molecules of low relative molecular mass that would not be considered macromolecules as specified in Definition 1.1. 

Due to their high molecular mass (and other reasons), the vast majority of mAbs that have been approved or are currently in clinical development are administered by intravenous (IV) infusion. This route allows the total dose to be available in the circulation, as F (the systemically available fraction of the dose) is, by definition, 1. In consequence, maximum concentrations in serum are rapidly observed, and are higher compared to those achieved by other routes. Therefore, adverse reactions after IV administration occur more often but are generally reversible. In addition, IV infusions represent the most inconvenient (they often require hospitalization) as well as time- and cost-consuming means of administration. Consequently, ex-travascular routes have been chosen as alternatives, including subcutaneous administration (SC e. g., adalimumab, efalizumab) and intramuscular administration (IM e.g., palivizumab) (Table 3.4). 

The most reactive in this reaction were N-phosphorylated salts of isoquinoline, which hetarylated indole even at room temperature. Pyridine and particularly quinoline are less reactive. With these heterocycles the reaction took place only in the presence of the more active dialkylphosphinic acid chlorides. The steric effects of the substituents at the phosphorus atom have a definite role. It was found that substituents with smaller molecular mass and less branched substituents made it possible to conduct the reaction under milder conditions and lead to an... 

The situation is different for aqueous species of humic substances, the organic matter in soil that is not identifiable as unaltered or partially altered biomass or as conventional biomolecules.21 Humic substances comprise organic compounds that are not synthesized directly to sustain the life cycles of the soil biomass. More specifically, they comprise polymeric molecules produced through microbial action that differ from biopolymers because of their molecular structure and their long-term persistence in soil. This definition of humic substances implies no particular set of organic compounds, range of relative molecular mass, or mode of chemical reactivity. What is essential is dissimilarity to conventional biomolecular structures and biologically refractory behavior. 

An earlier off-odor problem that surfaced was the presence of 4-phenyl-cyclohexene in styrene-butadiene coated paper (Koszinowski et al. 1980). This compound was created by a Diels-Alder condensation reaction involving a molecule of styrene and butadiene and is differentiated by its odor from the isomeric 3 and 1-phenyl-cyclohex-ene compounds which cannot be formed by such a condensation reaction. The recognition threshold of this compound in the headspace over an aqueous solution lies around a concentration of 10 pg/kg (10 ppb). The typical odor of this compound at concentrations of 4-phenyl-cyclohexene in paper over 4 mg/kg (4 ppm) is easily identified. AGC determination in this concentration range is also possible without difficulty and its identification with MS using the relative molecular mass of 158 and one of the retro Diels-Alder decomposition product fragments at m/e = 104 (styrene) and mJe = 54 (butadiene) is definitely possible. 

---