Macromolecule molecular weight

DRUG-CARRIER — soluble macromolecule - molecular weight ensuring access to the target tissue... 

Proteins are macromolecules (molecular weights from about 5000 to 106 [3]). There are thousands of different types of proteins, each with a particular biological function, often extremely specific. Thus, a particular enzyme will often recognize only one or a very narrow class of compounds as reactants and catalyze reaction of those to particular products. Other enzymes, typically those that catalyze hydrolysis or other degradative reactions, recognize a particular bond type but will act upon a broad class of reactants (substrates). These protein catalysts typically operate effectively at ambient temperature and pressure. Unique catalytic capabilities give enzymes their niche in bioprocessing. 

Fine colloids (including some macromolecules), molecular weight > 10 kD and size < 0.1 pm 2 - 3 05 O O 1 -. a o CO n < A N UWW dry weather UWWF beginning of rain UWWF wet weather NW wet weather - Spectra rather structured, except for natural water in wet weather (physical dispersion for the latter ones) - Presence of shoulders around 260-290 nm and around 225 nm for UWW and UWWF... 

Macromolecule Molecular Weight Mw Mw/Mn Molecular Diameter in Solution A. 

Macromolecule Molecular weight of the Blacromolecule to be separated Acrylamide in separating gel(%)... 

NMR spectroscopy has proved to be a powerful method for the elucidation of the structure of relatively small macromolecules (molecular weights of up to ca. 10,000 Da). In particular, this applies to RNA molecules for which X-ray crystallographic analyses are relatively rare, mainly due to difficulties with their crystallization. Under certain conditions a total structure elucidation of these (small) molecules in their native environment (aqueous solution) at atomic resolution is feasible by means of multidimensional NMR methods [4-10]. Moreover, even distinctly larger molecules, like whole tRNAs, can be at least partially cbar-acterized with reference to their structure, in particular secondary structure [11-14]. As detailed below, in certain cases NMR spectroscopy can also provide useful information for the... 

Most of the above analysis was carried out for macromolecules. One could also carry out an almost identical analysis for particles using the particle flux expression (7.3.198), as long as the particle dimensions are less than 0.1 pm. The following selectivity definitions have been used in FFF techniques for macromolecules (molecular weight M) and particles (particle diameter dp) ... 

Viscosity additives are aliphatic polymers of high molecular weight whose main chain is flexible. It is known that in a poor solvent, interactions between the elements making up the polymer chain are stronger than interactions between the solvent and the chain (Quivoron, 1978), to the point that the polymer chain adopts a ball of yarn configuration. The macromolecules in this configuration occupy a small volume. The viscosity of a solution being related to the volume occupied by the solute, the effect of polymers on the viscosity in a poor solvent will be small. 

In polymer solutions and blends, it becomes of interest to understand how the surface tension depends on the molecular weight (or number of repeat units, IV) of the macromolecule and on the polymer-solvent interactions through the interaction parameter, x- In terms of a Hory lattice model, x is given by the polymer and solvent interactions through... 

The successful preparation of polymers is achieved only if tire macromolecules are stable. Polymers are often prepared in solution where entropy destabilizes large molecular assemblies. Therefore, monomers have to be strongly bonded togetlier. These links are best realized by covalent bonds. Moreover, reaction kinetics favourable to polymeric materials must be fast, so tliat high-molecular-weight materials can be produced in a reasonable time. The polymerization reaction must also be fast compared to side reactions tliat often hinder or preclude tire fonnation of the desired product. 

Processes for HDPE with Broad MWD. Synthesis of HDPE with a relatively high molecular weight and a very broad MWD (broader than that of HDPE prepared with chromium oxide catalysts) can be achieved by two separate approaches. The first is to use mixed catalysts containing two types of active centers with widely different properties (50—55) the second is to employ two or more polymerization reactors in a series. In the second approach, polymerization conditions in each reactor are set drastically differendy in order to produce, within each polymer particle, an essential mixture of macromolecules with vasdy different molecular weights. Special plants, both slurry and gas-phase, can produce such resins (74,91—94). 

Polyamides, like other macromolecules, degrade as a result of mechanical stress either in the melt phase, in solution, or in the soHd state (124). Degradation in the fluid state is usually detected via a change in viscosity or molecular weight distribution (125). However, in the soHd state it is possible to observe the free radicals formed as a result of polymer chains breaking under the appHed stress. If the polymer is protected from oxygen, then alkyl radicals can be observed (126). However, if the sample is exposed to air then the radicals react with oxygen in a manner similar to thermo- and photooxidation. These reactions lead to the formation of microcracks, embrittlement, and fracture, which can eventually result in failure of the fiber, film, or plastic article. 

Reverse Osmosis and Ultrafiltration. Reverse osmosis (qv) (or hyperfiltration) and ultrafilttation (qv) ate pressure driven membrane processes that have become well estabUshed ia pollution control (89—94). There is no sharp distinction between the two both processes remove solutes from solution. Whereas ultrafiltration usually implies the separation of macromolecules from relatively low molecular-weight solvent, reverse osmosis normally refers to the separation of the solute and solvent molecules within the same order of magnitude in molecular weight (95) (see also Membrane technology). 

The lengths of these chains may be varied but in commercial polymers chains with from 1000 to 10000 of these methylene groups are generally encountered. These materials are of high molecular weight and hence are spoken of as high polymers or macromolecules. 

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