Rapid Intermediate

The conditions for generating Very Rapid are thus well defined and, in comparison with most other Mo(V) signals from enzymes, unique. It was suggested by Olson et al (1974) that Very Rapid represents an intermediate with a xanthine residue bound (covalently) to the enzyme molecule. Direct 

---

The Leggett Model simulates lead biokinetics in liver with two compartments the first simulates rapid uptake of lead from plasma and a relatively short removal half-life (days) for transfers to plasma and to the small intestine by biliary secretion a second compartment simulates a more gradual transfer to plasma of approximately 10% of lead uptake in liver. Different transfer rates associated with each compartment are calibrated to reproduce patterns of uptake and retention of lead observed in humans, baboons, and beagles following intravenous injection, as well as blood-to-liver concentration ratios from data on chronically exposed humans. Similarly, the Leggett Model simulates lead biokinetics in three compartments of soft tissues, representing rapid, intermediate, and slow turnover rates (without specific physiologic correlates). 

Insulin, a hormone produced by the pancreas, is essential for the metabolism of glucose, proteins, and fats. Insulins are classified on the basis of the duration of action as rapid-, intermediate-, or long-acting and on the basis of source or species, such as human or animal (beef, pork, and mixtures of beef and pork). Table 10.1 summarizes insulin preparations currendy available in the United States. 

Intranasal Snorted and absorbed across lining of nasal passages Rapid Intermediate... 

Insulin suspensions. When the hormone is injected as a suspension of insulin-containing particles, its dissolution and release in subcutaneous tissue are retarded (rapid, intermediate, and slow insulins). Suitable particles can be obtained by precipitation of apolar, poorly water-soluble complexes consisting of anionic insulin and cationic partners, e.g the polycationic protein protamine or the compound aminoqui-nuride (Surfen). In the presence of zinc and acetate ions, insulin crystallizes crystal size determines the rate of dissolution. Intermediate insulin preparations (NPH or isophane, lente or zinc insulin) act for 18 to 26 h, slow preparations (protamine zinc insulin, ultralente or extended zinc insulin) for up to 36 h. 

Articane Septocaine Rapid Intermediate Peripheral nerve block... 

Lidocaine Xylocaine Rapid Intermediate Infiltration Peripheral Nerve Block Epidural Spinal Transdermal Topical Sympathetic block Intravenous regional block... 

Tetracaine Pontocaine Rapid Intermediate to Long Topical Spinal... 

Protons on nitrogen may undergo rapid, intermediate, or slow exchange. If the exchange is rapid, the... 

The proton on a nitrogen atom may undergo rapid, intermediate, or slow exchange. If the exchange is rapid, the NH proton(s) is decoupled from the N atom and from protons on adjacent carbon atoms. The NH peak is therefore a sharp singlet, and the adjacent CH protons are not split by NH. Such is the case for most aliphatic amines.f... 

Figure 1.3 X-band EPR spectrum of the xanthine oxidase very rapid intermediate generated with 2-hydroxy-6-methylpurine as reducing substrate. Data were acquired at 150 K, 9.47 GHz and 10 mW microwave power. Note the high value for g, which has been used in conjunction with S hyperfine analysis to indicate the presence of a highly covalent Mo=S n bonding scheme in very rapid and, by inference, the oxidized Mo(vi) form of the enzyme. Adapted with permission from ref. 31. Copyright (1999) American Chemical Society.

In the latest development in effervescent forms, some formulations have been designed to control the rate of effervescence, so to obtain a rapid, intermediate, or slow rate. The rate control is strictly related to the acid-alkaline components ratio, but the chemical properties of the effervescent exdpients or their combinations can have influence on it, especially when a slow rate of effervescence is required. 

Figure 13 Proposed formation of a rapid intermediate in the oxidation of the hyper-reduced [3Fe-4S] cluster. (Adapted with permission from/. Am. Chem. Soc. 1998,120, 11994-11999. Copyright 1998 American Chemical Society.)...

If the reaction mechanism is nonlinear with respect to the intermediates, the solution of Equation 2.18 becomes more complicated and an iterative procedure is applied in most cases. It should be noticed that an assumption of each rapid intermediate reduces the number of adjustable rate parameters by one. For example, the application of the quasi-steady-state hypothesis in the system A R S implies that... 

---