Types of Flexibility

Besides investigating the basic binding mechanisms, the first key step toward modeling protein flexibility in structure-based design applications is to elucidate the various types of flexibility in proteins and their individual importance for ligand binding. 

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Because of the bulky neo stmcture in the middle of the molecule, this compound has enhanced hydrolytic stabiUty in addition to low volatihty. It is useful in many types of flexible foam, as well as in adhesives and epoxy- or phenoHc-based laminates. 

Grid-Type Couplings. Another type of flexible couplings, similar to disk couplings, is the grid type (Fig. 14c). These are appHed for moderate loads and allow parallel misalignment up to 0.1 mm (0.005 ia.). Lubrication is also requited. 

Various types of flexible connections are available for different purposes. Careful consideration is needed for suitability for purpose. General comments on connections available can be made. All connections should ... 

There are two types of flexible intermediate drives used to transmit torsional power belt drives and chain drives. Flexible belts are used in industrial power transmission applications primarily when the speeds of the driver and driven shafts must be different or when the shafts must be widely separated. The trend toward higher speed primary drivers and the need to achieve a slower, useful driven speed are additional factors favoring the use of belts. In addition to V-belts, there are round belts and flat belts. Chain drives are typically used in applications where space is limited or obstructions prevent direct coupling of machine-train components. 

Speed variation Variation in speed equates to a corresponding variation in torque. Most variable-speed applications require some type of flexible coupling capable of absorbing these torsional variations. 

Severity then, is an effective vehicle to vary the product distribution according to specific needs. This type of flexibility can be, and is often built into the design of an ethylene plant and adds relatively little to the cost of the plant. Another simple way to vary the by-product-to-ethylene ratio is to vary the extent of recycle cracking of ethane. 

Flame retardants are incorporated into the formulations in amounts necessary to satisfy existing requirements. There are four main types of flexible slabstock foam conventional, high resiliency, filled, and high load-bearing foam. 

Because TF1V Fluoroplastic is highly flexible, resistant to chemicals and automotive fuels, and has good barrier properties, it is used as a permeation barrier in various types of flexible hose in automotive applications and in the chemical process industry. Liners and tubing can be made from an electrostatic dissipative grade of TFIV, which is sometimes required for certain automotive applications.60... 

Comparing the various brands and types of flexible tubing is not unlike comparing a variety of stereos at competing stores. Because of the many different brands and models of tubing available, and because not every manufacturer uses the same... 

When ordering tubing, size is only one of several variables to consider. Two others are the tubing s physical characteristics (see Table 1.4) and its chemical resistance properties (see Table 1.5). Table 1.6 compares some of the advantages and disadvantages of the various types of flexible tubing. 

Glycidyl ethers of aliphatic polyols based on polyglycol, glycerin, and other polyols are flexible epoxy resins. They are used as reactive diluents and flexibihzers for solvent-free epoxy resin formulations. Epoxy-polyglycol resins that are produced from the reaction of epichlorohydrin and polyester polyols based on ethylene or propylene oxide are the most common of these types of flexible epoxy resins. Examples of typical commercial aliphatic epoxy resins are shown in App. C. 

Commercial products are available where n varies from 2 to 7. The flexible epoxy resins based on polyglycol also make excellent reactive diluents because they have a viscosity of 100 cP at 25°C. Table 4.4 shows the effect of two polyglycol diepoxides on the physical properties of a cured epoxy system. Another type of flexible epoxy resin is derived from dimerized unsaturated fatty acid, cashew nut oils, and other vegetable oils. Other flexible epoxy resins can be made with thiols, aliphatic acids, and hydroxyl-terminated compounds. Applications where flexible epoxy resins are valued include... 

It would seem that such broadened use of flexible plastics and rubbers in exterior-body structural members will compel the conclusion that high performance materials are needed. They must not only be relatively light, flexible, serviceable at temperature extremes, and easily fabricated and finished, but they must be as strong and as tough as possible. The public will demand this. One type of flexible synthetic polymer which meets these requirements very well indeed is the thermoplastic urethane elastomers which have already proved themselves in flexible front ends, sight shields, and fascia in production model automobiles. 

Isomers that differ by their chemical constitution are constitutionally isomeric. As traditionally defined, stereoisomers are molecules with the same chemical constitution that differ with respect to the relative spatial arrangement of their constituent atoms. Since many types of flexible molecules exist whose shape rapidly change with time and that are not adequately representable by any geometric model, stereoisomers must be defined as follows, without reference to molecular geometry ... 

Silicone rubbers, such as General Electric RTV, represent a useful type of flexible adhesive. They can be clear or opaque, are fairly inert chemically, and some are usable up to 300°C or above. These silicones are just poured or extruded from a tube, and no heat cure is required since they cure by air drying. The resulting seals are not mechanically strong but will provide protection against water and oil. 

M. Ravey and E. M. Pearce, Elexible polyurethane foam. 1. Thermal decomposition of a polyether-based, water-blown commercial type of flexible polyurethane foam, J. Appl. Polym. Sci., 63, 47-74 (1997). 

Work from a different laboratory focuses on the synthesis and photophysical properties of Ceo-based porphyrin dyads with a variety of linkers [367-371], These include new types of flexible polyether linkers (30) [367, 368], rigid steroid linkers [370] as well as novel doubly linked porphyrins [369, 371], which provide the means for a parachute-shaped dyad (e.g., ZnP-Ceo (29) and H2P-C60 (28)). In both para-... 

In the second type of semiflexible polymer molecule, rigid units are interspersed with flexible ones. Some examples of molecules of this kind are given in Chapter 11. The freely jointed chain model might be a suitable model for such semiflexible polymers. If a persistently flexible molecule and a freely jointed molecule are characterized by the same values of L and Xp (or, equivalently, of bx and Nk), then the gross statistical measures of the coil dimensions of the two such isolated chains will be the same, despite the differences in the type of flexibility. 

Fig. 3 Types of large volume parenterals. These represent the various types of flexible intravenous bag systems (A) Lifecare by Abbott Laboratories (B) Representative vial and flexible IV bag system, such as the Add-Vantage — Abbott Laboratories or Mini-Bag Plus System —Baxter Healthcare (C) Excel —B. Braun Medical and (D) Viaflex —Baxter Healthcare. These bags contain either polyvinyl chloride (Lifecare or Viaflex) or polyolefin (Excel).

There are two main types of flexible foam slabstock polyester-based foams, used for technical and high elongation grade laminates or textiles and polyether-based foams used for upholstery, HR, and flame retardance. By varying the type of polyester or polyether, the length of the polyol chain, the structure and size of the hard segment, and the amount of blowing, the foam can be tailored to meet the required specifications. ... 

Therefore, admixture studies are performed on parenteral drugs with commonly used intravenous diluents. Studies are performed by preparing admixtures of the drug product with various diluents in an appropriate type of flexible intravenous bag. Initial samples are taken for analysis before the bags are stored in temperature-controlled stability chambers. Subsequent samples may be pulled at 6-, 12-, 24-, 48-, and 72-h time points. The analytical tests commonly performed include visual appearance, pH, and HPLC assay. Degradation products are not commonly tested unless the method has been previously evaluated for specificity and stability-indicating ability with a particular intravenous diluent. This is necessary because there may be differences in the stability profile of the product in its original formulation compared to the admixture solution. Formation of any particulate matter is detected by visual... 

One type of flexible design is the group sequential design (23). Such a design typically includes one or more preplanned interim analyses. Based on the results of the interim analysis, a preplanned action is taken. Most commonly these actions include ... 

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