Subcellular range

Some of the radionuclides emitting electrons of subcellular range, which are of potential utility for radionuclide therapy, are given in Table 46.8. Because of this very short range. 

Selected radionuclides emitting electrons of subcellular range... 

SARA is a scaffolding protein that regulates the subcellular localization of inactivated R-Smads, potentially scaffolding the TGF-P receptor kinase to the Smad 2 substrate. Filamins are a family of actin polymerization proteins that also form scaffolds for a range of signaling proteins including SAP kinases such as MKK-4, small GTPases Rho and Ras, as well as Smad 2 and Smad 5. 

UV irradiation of this bacterial cells using a broadband mercury-quartz lamp through an interference filter (bandwith 254 nm), provided preferential DNA damage with minimal effects on other subcellular structures. The exposure time ranged from 0 to 180 minutes in increments of 60 minutes, which gave total dose of UV exposure 1.21, 2.43 and 3.64 J/ m. ... 

Efficacy. A relative concept referring to the ability of a medicine to elicit a beneficial clinical effect. This may be measured or evaluated using objective or subjective parameters, and in terms ranging form global impressions to highly precise measurements. Efficacy is assessed at one or more levels of organization (e.g., subcellular, cellular, tissue, organ, whole body) and may be extrapolated to other levels. 

In contrast to many chemotherapeutic agents in cancer therapy, boron compounds for BNCT do not require a tumoricidal action in their own right. For their successful application in the therapy of patients, it is important to deliver, to the tumor, a radiation dose which is higher than the radiation dose to the surrounding tissue. The demonstration that this is actually achieved lies ultimately in the treatment of the tumor in question. Because of the short range of the particles produced in the 10B(n,a)7Li reaction, it is very important where, on a cellular and subcellular dimension, the neutron capture reaction takes place. Different methods for boron detection and quantification give different resolution of the boron distribution. It is instructive to compare these methods, both for their precision and lower detection limits, as well as for their ability to yield an image of the boron distribution in tissue (Table 2.2-1). 

The intracellular localization of carboxylesterases is predominantly microsomal, the esterases being localized in the endoplasmic reticulum [73] [79] [93], They are either free in the lumen or loosely bound to the inner aspect of the membrane. The carboxylesterases in liver mitochondria are essentially identical to those of the microsomal fraction. In contrast, carboxylesterases of liver lysosomes are different, their isoelectric point being in the acidic range. Carboxylesterase activity is also found in the cytosolic fraction of liver and kidney. It has been suggested that cytosolic carboxylesterases are mere contaminants of the microsomal enzymes, but there is evidence that soluble esterases do not necessarily originate from the endoplasmic reticulum [94], In guinea pig liver, a specific cytosolic esterase has been identified that is capable of hydrolyzing acetylsalicylate and that differs from the microsomal enzyme. Also, microsomal and cytosolic enzymes have different electrophoretic properties [77]. Cytosolic and microsomal esterases in rat small intestinal mucosa are clearly different enzymes, since they hydrolyze rac-oxazepam acetate with opposite enantioselectivity [95], Consequently, studies of hydrolysis in hepatocytes reflect more closely the in vivo hepatic hydrolysis than subcellular fractions, since cytosolic and microsomal esterases can act in parallel. 

Microsomes are a membrane fraction prepared from subcellular structures containing cytochrome P450 and its reductase. Cyt P450 reductase uses NADPH as an electron source and can bring about the one-electron reduction of a range of xenobiotics. 

Both actin and myosin are present in nonmuscle cells. Actin is a highly conserved protein in organisms ranging from cellular slime molds to humans, whereas myosin is less well conserved. Within nonmuscle cells these two proteins are involved in such processes as cell movement, the transport of membrane-bound subcellular organelles around the cell on actin tracks, and cell division (see Topic A2). 

This work led to the important conclusion that the capacitance of all biological membranes, including cellular membranes and those of subcellular organelles, such as mitochondria, is of the order of 1 yF/cm. This value is apparently independent of frequency in the total RF range at low audio frequencies, capacitance values increase with decreasing frequencies due to additional relaxation mechanisms in or near the membranes Q, 26). These mechanisms will not be discussed here and have been summarized elsewhere (1, 26). 

All SABATH proteins characterized so far contain between 357 and 389 amino acids, and the molecular mass of the subunit ranges from 40-49 kDa. Size exclusion chromatography, performed with some of these enzymes, has revealed that the molecular mass of the native enzymes is roughly 80 kDa, indicating a dimeric structure. None of the SABATH proteins identified thus far have any obvious subcellular targeting signals. Cytosolic localization was experimentally confirmed for two of these enzymes, BAMT and CaMXMT.57,59... 

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