(+)-Bornyl piperate, a new monoterpene ester from Piper aff. pedicellatum roots

A new monoterpene ester, (+)-bornyl piperate was isolated from the underground roots of Piper aff. pedicellatum and its structure was elucidated on the basis of spectroscopic evidence and confirmed by X-ray analysis. The compound crystallizes in the triclinic space group P1 with a=7.3232(4) A, b=11.4705(7) A, c=23.2520(14) A, V=1943.6(2) A(3). This compound showed an antituberculosis activity against Mycobacterium tuberculosis (H(37)Ra strain) with the minimum inhibitor concentration (MIC) of 25 microg/ml.     

Probing DNA selectivity of ruthenium metallointercalators using ESI mass spectrometry

ESI mass spectra show that up to five ruthenium molecules can bind non-covalently to double stranded 16mer DNA, and provide information on the relative affinity and DNA sequence selectivity of different ruthenium complexes.     

Comparison of mass spectrometry and other techniques for probing interactions between metal complexes and DNA

Electrospray ionization mass spectrometry (ESI-MS) was used to study the binding interactions of two series of ruthenium complexes, [Ru(phen) 2L] (2+) and [RuL' 2(dpqC)] (2+), to a double stranded DNA hexadecamer, and derive orders of relative binding affinity. These were shown to be in good agreement with orders of relative binding affinity derived from absorption and circular dichroism (CD) spectroscopic examination of the same systems and from DNA melting curves. However, the extent of luminescence enhancement caused by the addition of DNA to solutions of the ruthenium complexes showed little correlation with orders of binding affinity derived from ESI-MS or any of the other techniques. Overall the results provide support for the validity of using ESI-MS to investigate non-covalent interactions between metal complexes and DNA.     

Sequential injection titration with spectrophotometric detection for the assay of acidity in fruit juices.

A simple sequential injection analysis (SIA) with spectrophotometric detection for an assay of acidity in fruit juice was investigated. An alkaline reagent (sodium hydroxide), a sample and an indicator (phenolphthalein) were first aspirated and stacked as adjacent zones in a holding coil. With flow reversal through a reaction coil to the detector, zone penetration occurred, leading to a neutralization reaction that caused a decrease in the color intensity of the indicator being monitored for absorbance at 552 nm. The effects of various parameters were studied. Linear calibration graphs for acidities of 0.2 - 1.0 and 0.5 - 2.5% w/v citric acid as a standard, with a relative standard deviation of 1% (acidity of 0.3 - 0.6% w/v as citric acid, n=11) and a sample throughput of 30 samples h(-1), were achieved. The developed method was validated by a standard titrimetric method for assaying the acidity of fruit juice samples.     

Synthetic approaches to unsaturated five-membered heterocycles containing both ring and side-chain phosphorus atoms

The syntheses of several structurally interesting 2-diphenylphosphinyl-substituted 2-phospholenes and phospholanes are reported together with a discussion of the ₃₁P and 13° C nmr spectral properties of these compounds. Several of these syntheses were found to be highly stereoselective and the potential of some of the products of these reactions as precursors to phosphole derivatives bearing phosphorus-containing side-chains has also been explored. A new, and possibly general, route to 4-oxo-2-phospholene oxides or sulfides from the corresponding 4-methylene compounds is also reported. This route involves an unusual free-radical catalyzed oxidative cleavage of the 4-methylene group by molecular oxygen and a probable mechanism for this reaction is proposed.     

An unusual synthesis of 2,3-dihydrophosphindole 1-oxides

A very simple route to dimeric phosphole oxides is reported as is the pyrolytic decomposition of these phosphorus-bridged dimers. Like similar dimeric phosphole sulfides, these phosphole oxide dimers readily eliminate the bridging phosphorus grouping upon strong heating but, unlike the analogous sulfides, hydrogen transfer to give a 2,3-dihydrophosphindole 1-oxide rather than hydrogen elimination to give the fully unsaturated phosphindole oxide occurs. This hydrogen transfer is shown to be non-stereospecific and some mechanistic implications of this are briefly discussed.     

DNA hybridization enhancement using piezoelectric microagitation through a liquid coupling medium

In conventional DNA microarray hybridization, delivery of target cDNAs to surface-bounded probes depends solely on diffusion, which is notoriously slow, and thus typically requires 6-20 h to complete. In this study, piezoelectric microagitation through a liquid coupling medium is employed to enhance DNA hybridization efficiency and the results are compared with the standard static hybridization method. DNA hybridization was performed in a sealed aluminium chamber containing DNA microarray glass chip, coupling medium and piezoelectric transducers. 3×SSC (Saline Sodium Citrate) was used as a coupling medium to prevent overheating of the piezoelectric transducers and to effectively transmit ultrasonic wave to the glass chip. Flow visualization using fluidic dye and velocimetry (PTV) technique was applied to observe fluid transport in the hybridization chamber. It was revealed that the dye solution was homogeneously distributed within 10 min under dynamic agitation while it took over 1 h to reach the same level of homogeneity in static condition. Plasmodium falciparum DNA microarrays and total RNA extracted from parasite cells were used as a model for DNA microarray experiments. It was found that the required hybridization time may be substantially reduced from 16 h to 4 h by the use of dynamic hybridization scheme. With the same hybridization time of 16 h, dynamic hybridization resulted in higher fluorescent signals of ～33% and ～24% compared to static hybridization in Cy3 and Cy5 channels, respectively. Additionally, good/effective spots, some of which were not formed by static method, were enhanced and distributed more uniformly over the microarray. Therefore, the developed dynamic hybridization with integrated piezoelectric microagitation platform is highly promising for DNA analysis in molecular biology and medical applications.