The hemoglobin Brockton variant (beta 138 (H16) Ala----Pro) has decreased intrinsic oxygen affinity similar to Hb A. However, x-ray crystallographic data indicate that the substitution at position beta 138 does not disrupt important polar interactions that contribute to cooperative oxygenation. This is consistent with the absence of abnormalities in blood and hemolysate oxygen affinity measurements.
Function
In mathematics, the beta function is a real-valued function defined on an infinite dimensional array, B(p, q). It can be written as f(p, q) = 2 ** (p 1) / 4 ** (q 1). It has many uses in physics and functional analysis, including the representation of Regge trajectories.
The beta function tells us that the coupling increases with increasing energy scale and that QED becomes strongly coupled at high energies, resulting in a Landau pole. This result is quite contrary to the classical expectation that QED should be scale invariant.
It is also the basis for the Pochhammer contour integral, a useful tool in the study of the dynamics of quantum systems. The beta function is related to the incomplete gamma function by the relationship that divides both sides of the integral by G(z 1 + z 2), the digamma function. The complete Beta138 gamma function is defined as f(z 1 + z 2) / f(z 2 + z 2). The incomplete beta function can be computed by a continued fraction expansion.
Structure
The transforming growth factor beta (TGFb) pathway orchestrates a wide range of biological processes - from bone development to reproduction. Hence, the pathway is a subject of intense research and therapeutic pursuits. Structural techniques have provided a wealth of information regarding several layers of the pathway.
A series of crystal structures for the type II receptor Alk5 have been resolved, providing a structural basis for ligand binding and signaling. The structure shows that an arginine residue, Glu245 of the aC helix, forms a salt bridge with a key FKBP12 lysine at b3. This salt bridge breaks when the kinase domain is bound by a ligand and allows the activation loop to engage in the phosphorylation reaction.
The Hemoglobin Brockton variant, which has a mutation at the beta 138 amino acid position, displays reduced oxygen affinity. X-ray crystallographic studies have shown that this defect is associated with the failure of a critical buried hydrogen bond to form between Pro 138 and Val 134 beta.
Electrophoretic Mobility
In capillary electrophoresis, the efficiency of separation depends on a number of factors including the voltage applied to the capillary, the viscosity of the medium and the size and charge of the analyte. The larger the analyte, the higher its molecular weight, the faster it will move through the gel.
As the gel fills up with solute, its hydrodynamic radius decreases. This is related to its size and charge, and the intrinsic electrophoretic mobility (mep) of a neutral analyte is given by Equation 12.7.10:
In general, m tends to zero for a charged analyte but can have positive or negative values for neutral solutes. The intrinsic electrophoretic mobility increases with the concentration of salt in the sample and can also be affected by the pH of the buffer solution or the temperature.
Molecular Weight
CD138 (syndecan 1) is a 90 kDa glycosylated protein that is present in the plasma cells of normal individuals. It is expressed mainly in differentiating keratinocytes and can also be detected in tumor cells of various origin. It binds a number of cytokines and modulates their activity. Serum levels of soluble CD138 are used as a marker for carcinogenesis. This antibody reacts with human syndecan-1 and stains formalin-fixed, paraffin-embedded human cancer tissues and cells of normal tissue origin by immunohistochemistry. It demonstrates only very weak staining of FFPE tissue sections after heat induced epitope retrieval. The Brockton hemoglobin variant, associated with mild anemia, has normal oxygen affinity in blood and hemolysates, and it has the same electrophoretic mobility as Hb A. X-ray crystallographic studies suggest that the introduction of proline into the H helix at beta 138 does not disrupt critical inter and intrasubunit hydrogen bonds and salt bridges that are essential for oxygen binding.
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