Sequence-dependent cluster analysis of biomineralization peptides

A reliable and statistically valid classification of biomineralization peptides is herein presented. 27 biomineralization peptides (BMPep) were randomly selected as representative samples to establish the classification system using k-means method. These biomineralization peptides were either discovered through isolation from various organisms or via phage display. Our findings show that there are two types of biomineralization peptides based on their length, molecular weight, heterogeneity, and aliphatic residues. Type-1 BMPeps are more commonly found and exhibit higher values for these significant clustering variables. In contrast are the type-2 BMPeps, which have lower values for these parameters and are less common. Through our clustering analysis, a more efficient and systematic approach in BMPep selection is possible since previous methods of BMPep classification are unreliable.

Identification of a new component in the murine Ia molecular complex.

In this report, we describe a previously unidentified component in the murine Ia antigen complex. SDS-PAGE analysis of anti-Ia immunoprecipitates prepared from spleen cells biosynthetically labeled with 35S-sulfate showed no detectable incorporation of 35SO4 into alpha, beta, or Ii chains but did not reveal the presence of a novel sulfate-bearing molecule of considerable molecular weight heterogeneity (46-69-kdaltons). The 46-69-kdalton molecule could be precipitated with monoclonal antibodies specific for I-A, I-E, and Ii glycoproteins but was not seen in control precipitates, nor in association with IgG or class I MHC molecules. Preliminary biochemical characterization indicated that the 46-69-kdalton product is extremely polydisperse, both in charge and apparent molecular weight, is sensitive to proteases, and bears the sulfate moiety on a large pronase-resistant structure. These results suggested this component might be a proteoglycan. Definitive identification of this component as a proteoglycan was accomplished by selective enzymatic degradation experiments which showed that the sulfate-bearing component of the 46-69-kdalton molecule is chondroitin 6-sulfate.

Heterogeneity of immunoreactive calcitonin in human milk

Immunoreactive calcitonin (ICT) has been detected in human milk by radioimmunoassay (RIA), using antibodies raised against synthetic human calcitonin (hCT). The level of ICT was 10–40 times higher than the reference level of human serum. Gel chromatography of human milk disclosed a molecular weight heterogeneity of ICT, with at least two forms larger than the monomer (Mr > 70 000 and 30 000 approximately). The 30 000 peak constituted the major fraction of ICT. No detectable amount of ICT was coeluted with [125I]CT. Reduction with disulphide cleaving agents, denaturation or acidification did not alter the gel chromatographic properties of ICT, while tryptic digestion caused partial degradation of ICT and formation of new ICT molecules with an approximate molecular weight of 6000.