Urinary pregnanediol and creatinine excretion in the female of menstrual age

The urinary pregnanediol and creatinine excretions in females of menstrual age were correlated. The high degree of correlation found allows the use of the pregnanediol/creatinine ratio of the first-morning voided urinary specimen in calculating, with a fair degree of precision, the 24-hr. pregnanediol excretion.     

Infectious Disease Markers in Blood Donors

Background

The infectious disease markers for which blood donors are screened include anti-human immunodeficiency virus (HIV), hepatitis B surface antigen (HBsAg), anti-hepatitis C virus (HCV), rapid plasma reagin (RPR) card test for syphilis and malarial parasites.

Methods

A total of 6751 donors were screened over three years to assess the prevalence of infectious disease markers. Screening for anti-HIV I and II, HBsAg and anti-HCV was carried out by enzyme linked immunosorbent assay (ELISA). Syphilis was tested using RPR card test. Malarial parasite was tested by detection of genus specific plasmodium lactate dehydrogenase.

Result

The overall seropositivity for anti-HIV I and II was nine (0.13%), for HBsAg 67 (0.99%), for anti-HCV 13 (0.19%) and for syphilis 42 (0.62%). No sample showed malarial parasites. There was no significant difference (p>0.05) in the seropositivity of various markers between voluntary and replacement donors. There was a significant decline (p<0.05) in the prevalence of seropositivity for HCV and syphilis, but not for HIV and HBsAg over the three year period of the study.

Conclusion

The prevalence of infectious disease markers was similar to that reported by other studies. However, no significant difference was seen in the marker positivity in voluntary and replacement donors, which is at variance from other studies.Key Words: Infectious disease, Blood donors     

Origin of Two Modes of Non-isothermal Crystallization of Glasses Produced by Milling

Purpose  

To mechanistically explain the origin of two distinct non-isothermal crystallization modes, single-peak (unimodal) and two-peak (bimodal), of organic glasses.     

Profoundly improving flow properties of a cohesive cellulose powder by surface coating with nano-silica through comilling

Poor flow properties hinder the easy handling of powders during industrial-scale processing. In this work, we show that powder flow can be substantially improved by reducing the cohesion of powders by coating them with nanosized guest particles. We further show that comilling is an efficient process for nanocoating. We have systematically investigated the effects of total number of comilling cycles (10-70 cycles) and silica loading (0-1.0 wt %) on the flow behavior of a highly cohesive and poorly flowing grade of microcrystalline cellulose powder (Avicel PH105). Optimum flow enhancement has been achieved with 1.0 wt % silica loading at 40 comilling cycles. The flow properties of nanocoated Avicel PH105 are comparable to those of Avicel PH102, which exhibits adequate flowability for processing on a high-speed tablet press. Comilling is fast and suitable for continuous processing. It shows potential for addressing industrial powder handling problems caused by poor powder flow properties.     

Dissociation kinetics of RepA dimers: implications for mechanisms of activation of DNA binding by chaperones

Background :  The replication initiator of plasmid P1, RepA, binds DNA as monomer. The binding is stimulated by the chaperones DnaJ, DnaK and GrpE of Escherichia coli . Two models of chaperone action have been proposed. (i) Chaperones dissociate RepA dimers, which are inactive in DNA binding, into active monomers. (ii) The dissociation occurs spontaneously but the monomeric products require the chaperones for refolding into the active form. The latter model was based on the observation that RepA diluted 1000-fold below the K _D for dimer dissociation, still required the chaperones for DNA binding.
Results :  We have confirmed that under the condition of DNA binding experiments, the RepA dimers dissociate reversibly into monomers with a K _D value of 1.1 ± 0.1 μ m . In the vicinity of this concentration, the sedimentation coefficient of RepA was concentration dependent, allowing estimation of s _20,w coefficients for the RepA monomer (2.95 S) and dimer (4.01 S). Dynamic light scattering experiments indicated an increase of the monomer fraction within 5 min of RepA dilution. Circular dichroism (CD) measurements were consistent with these results.
Conclusion :  RepA monomerization is efficient without the mediation of chaperones. They are required to activate RepA most likely because they are needed to re-fold RepA monomers.     

Ultra-fast excited state dynamics in green fluorescent protein: multiple states and proton transfer.

The green fluorescent protein (GFP) of the jellyfish Aequorea Victoria has attracted widespread interest since the discovery that its chromophore is generated by the autocatalytic, posttranslational cyclization and oxidation of a hexapeptide unit. This permits fusion of the DNA sequence of GFP with that of any protein whose expression or transport can then be readily monitored by sensitive fluorescence methods without the need to add exogenous fluorescent dyes. The excited state dynamics of GFP were studied following photo-excitation of each of its two strong absorption bands in the visible using fluorescence upconversion spectroscopy (about 100 fs time resolution). It is shown that excitation of the higher energy feature leads very rapidly to a form of the lower energy species, and that the excited state interconversion rate can be markedly slowed by replacing exchangeable protons with deuterons. This observation and others lead to a model in which the two visible absorption bands correspond to GFP in two ground-state conformations. These conformations can be slowly interconverted in the ground state, but the process is much faster in the excited state. The observed isotope effect suggests that the initial excited state process involves a proton transfer reaction that is followed by additional structural changes. These observations may help to rationalize and motivate mutations that alter the absorption properties and improve the photo stability of GFP.     

P1 plasmid replication: multiple functions of RepA protein at the origin.

Replication functions of a bacteriophage P1 miniplasmid are carried on a 1.2-kilobase pair (kb) segment that can be subdivided into a 245-base pair (bp) replication origin and a 959-bp region that encodes a protein required for replication (RepA). The origin region contains five 19-bp direct repeats. By using primer extension and gene-fusion assays, we mapped the promoter of the repA gene within the repeated sequences and showed that the promoter is repressed by RepA. Regulation of RepA synthesis is apparently achieved by the binding of RepA to the repeat sequences. This regulation might be a key step in the replication-control circuit, as we found that overproduction of RepA (from a foreign promoter) inhibits replication. Thus, in addition to being an autoregulated activator of replication, the protein also can have a negative regulatory role.