01761nas a2200205 4500008004100000022001400041245007300055210006900128260011000197300001400307490000700321520099400328100001801322700001901340700002501359700001901384700001901403700003001422856010301452 2007 eng d a0959-942800aEffect of halogen addition to monolayer protected gold nanoparticles0 aEffect of halogen addition to monolayer protected gold nanoparti aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcFEB a1614-16190 v173 a

The effects of N-halosuccinimide and halogen addition to monolayer protected gold nanoparticles (Au NPs) dispersed in organic media are described. Contrary to the expectation that nanoparticles dispersed in organic media are stable against aggregation, N-iodosuccinimide addition induced aggregation of octadecylamine capped gold nanoparticles in chloroform or toluene. It was observed that even KI and CuI addition could bring about the aggregation though they are very sparingly soluble in organic solvents. It was also found that even molecular iodine could bring about the above mentioned aggregation. Interestingly, when CuI is used the aggregated structures readily convert to very thin flat nanostructures upon exposure to an electron beam or UV irradiation. In fact when the aggregation is induced by the addition of KI or N-iodosuccinamide we do not see the flattening of the aggregated structures exemplifying the important role of Cu ions in making these flat structures.

1 aSingh, Sanjay1 aPasricha, Renu1 aBhatta, Umananda, M.1 aSatyam, P., V.1 aSastry, Murali1 aPrasad, Bhagavatula L. V. uhttp://library.ncl.res.in/content/effect-halogen-addition-monolayer-protected-gold-nanoparticles-002717nas a2200265 4500008004100000022001400041245018300055210006900238260007700307300001400384490000600398520169400404653001702098653001902115653001802134653002402152653001102176100002302187700001802210700003002228700002302258700001902281700002402300856012702324 2008 eng d a1439-422700aExtracellular synthesis of crystalline silver nanoparticles and molecular evidence of silver resistance from morganella sp.: towards understanding biochemical synthesis mechanism0 aExtracellular synthesis of crystalline silver nanoparticles and  aPO BOX 10 11 61, D-69451 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcJUN a1415-14220 v93 a

There has been significant progress in the biological synthesis of nanomaterials. However, the molecular mechanism of synthesis of such bio-nanomaterials remains largely unknown. Here, we report the extracellular synthesis of crystalline silver nanoparticles (AgNPs) by using Morganella sp., and show molecular evidence I of silver resistance by elucidating the synthesis mechanism. The AgNPs were 20 +/- 5 nm in diameter and were highly stable at 1 room temperature. The kinetics of AgNPs formation was investigated. Detectable particles were formed after on hour of reaction, and their production remained exponential up to 18 h, and saturated at 24 h. Morganella sp. was found to be highly resistant to silver cations and was able to grow in the presence of more than 0.5 mm AgNO3. Three gene homologues viz. silE, silP and silS were identified in silver-resistant Morganella sp. The homologue of silE from Morganella sp. showed 99% nucleotide sequence similarity with the previously reported gene, silE, which encodes a periplasmic silver-binding protein. The homologues of silP and silS were also highly similar to previously reported sequences. Similar activity was totally absent in closely related Escherichia coli; this suggests that a unique mechanism of extracellular AgNPs synthesis is associated with silver-resistant Morganella sp. The molecular mechanism of silver resistance and its gene products might have a key role to play in the overall synthesis process of AgNPs by Morganella sp. An understanding of such biochemical mechanisms at the molecular level might help in developing an ecologically friendly and cost-effective protocol for microbial AgNPs synthesis.

10aBiosynthesis10aMorganella sp.10aNanoparticles10asil gene homologues10aSilver1 aParikh, Rasesh, Y.1 aSingh, Sanjay1 aPrasad, Bhagavatula L. V.1 aPatole, Milind, S.1 aSastry, Murali1 aShouche, Yogesh, S. uhttp://library.ncl.res.in/content/extracellular-synthesis-crystalline-silver-nanoparticles-and-molecular-evidence-silver-002077nas a2200253 4500008004100000022001400041245019000055210006900245260007900314300001200393490000800405520106000413653002801473653002501501653002401526653002101550653002701571100001601598700001801614700001901632700002101651700002001672856013101692 2009 eng d a0273-228900aEffect of cultural conditions and media constituents on production of penicillin V acylase and CTAB treatment to enhance whole-cell enzyme activity of rhodotorula aurantiaca (NCIM 3425)0 aEffect of cultural conditions and media constituents on producti a999 RIVERVIEW DRIVE SUITE 208, TOTOWA, NJ 07512 USAbHUMANA PRESS INCcJUN a463-4720 v1573 a

Penicillin V acylase (PVA) is a pharmaceutically important enzyme as it plays a vital role in the manufacture of semi-synthetic beta-lactam antibiotics. Rhodotorula aurantiaca (NCIM 3425) produced high levels of intracellular penicillin V acylase after 18 h at pH 8.0 and temperature 27 degrees C. Fructose was the best carbon source for PVA production, whereas tryptone was the best nitrogen source to produce the enzyme up to 170 and 1,088 IU/l of culture, respectively. Additionally, the cell-bound PVA activity was enhanced on treatment with cationic detergent. Whole-cell activity was found to be doubled (204%) on treatment of 0.01 g dry weight of cells with 50 mu g/ml solution of N-cetyl-N,N,N-trimethylammoniumbromide at pH 8.0 for 1 h at room temperature. Atomic force microscopy images of permeabilized cells show perturbation in the cell wall and offer first-ever visual illustration of surface structure modifications that occur during permeabilization of R. aurantiaca cells leading to enhancement in activity of intracellular enzyme.

10aAtomic force microscopy10aIntracellular enzyme10aPenicillin Vacylase10aPermeabilization10aRhodotorula aurantiaca1 aKumar, Atul1 aSingh, Sanjay1 aPoddar, Pankaj1 aPrabhune, Asmita1 aPundle, Archana uhttp://library.ncl.res.in/content/effect-cultural-conditions-and-media-constituents-production-penicillin-v-acylase-and-ctab-0