Rapid detection of an anthrax biomarker by surface-enhanced Raman spectroscopy

A rapid detection protocol suitable for use by first-responders to detect anthrax spores using a low-cost, battery-powered, portable Raman spectrometer has been developed. Bacillus subtilis spores, harmless simulants for Bacillus anthracis, were studied using surface-enhanced Raman spectroscopy (SERS) on silver film over nanosphere (AgFON) substrates. Calcium dipicolinate (CaDPA), a biomarker for bacillus spores, was efficiently extracted by sonication in nitric acid and rapidly detected by SERS. AgFON surfaces optimized for 750 nm laser excitation have been fabricated and characterized by UV-vis diffuse reflectance spectroscopy and SERS. The SERS signal from extracted CaDPA was measured over the spore concentration range of 10(-14)-10(-12) M to determine the saturation binding capacity of the AgFON surface and to calculate the adsorption constant (Kspore=1.7 x 10(13) M(-1)). At present, an 11 min procedure is capable of achieving a limit of detection (LOD) of approximately 2.6 x 10(3) spores, below the anthrax infectious dose of 10(4) spores. The data presented herein also demonstrate that the shelf life of prefabricated AgFON substrates can be as long as 40 days prior to use. Finally, these sensing capabilities have been successfully transitioned from a laboratory spectrometer to a field-portable instrument. Using this technology, 10(4) bacillus spores were detected with a 5 s data acquisition period on a 1 month old AgFON substrate. The speed and sensitivity of this SERS sensor indicate that this technology can be used as a viable option for the field analysis of potentially harmful environmental samples.     

Analysis of the 5p6p configuration of Xe V

The spectrum of four times ionized Xenon (XeV), has been observed in the 500–6800 Å range and 84 new lines have been identified as transitions between levels of 5s5p ³, 5s ²5p5d, 5s ²5p6s, 5s ²5p ², and 5s ²5p6p configurations. Nine new levels belonging to the configuration 5p6p have been determined. The results of this analysis are supported by Hartree-Fock calculations. The configurations are interpreted by fitting the theoretical energy parameters to the observed levels using least-squares techniques.     

Conformation of DNA modified by monofunctional Ru(II) arene complexes: recognition by DNA binding proteins and repair. Relationship to cytotoxicity

We analyzed DNA duplexes modified at central guanine residues by monofunctional Ru(II) arene complexes [(eta(6)-arene)Ru(II)(en)(Cl)](+) (arene = tetrahydroanthracene or p-cymene, Ru-THA or Ru-CYM, respectively). These two complexes were chosen as representatives of two different classes of Ru(II) arene compounds for which initial studies revealed different binding modes: one that may involve DNA intercalation (tricyclic-ring Ru-THA) and the other (mono-ring Ru-CYM) that may not. Ru-THA is approximately 20 times more toxic to cancer cells than Ru-CYM. The adducts of Ru-THA and Ru-CYM have contrasting effects on the conformation, thermodynamic stability, and polymerization of DNA in vitro. In addition, the adducts of Ru-CYM are removed from DNA more efficiently than those of Ru-THA. Interestingly, the mammalian nucleotide excision repair system has low efficiency for excision of ruthenium adducts compared to cisplatin intrastrand crosslinks.     

Gold(I) Complexes with the nido-Diphosphino Ligand [7,8-(Ph(2)P)(2)-7,8-C(2)B(9)H(10)](-). Preparation of the First Metallocarborane Complex of this Ligand. Crystal Structures of [Au{(PPh(2))(2)C(2)B(9)H(10)}(PPh(3))].CH(2)Cl(2) and [Au(2){(PPh(2))(2)C(2)B(9)H(10)}(2){(PPh(2))(2)(CH(2))(3)}].3Me(2)CO

The reaction of [AuCl(PR(3))] with [1,2-(Ph(2)P)(2)-1,2-C(2)B(10)H(10)] in refluxing ethanol proceeds with partial degradation (removal of a boron atom adjacent to carbon) of the closo species to give [Au{(PPh(2))(2)C(2)B(9)H(10)}(PR(3))] [PR(3) = PPh(3) (1), PPh(2)Me (2), PPh(2)(4-Me-C(6)H(4)) (3), P(4-Me-C(6)H(4))(3) (4), P(4-OMe-C(6)H(4))(3) (5)]. Similarly, the treatment of [Au(2)Cl(2)(&mgr;-P-P)] with [1,2-(Ph(2)P)(2)-1,2-C(2)B(10)H(10)] under the same conditions leads to the complexes [Au(2){(PPh(2))(2)C(2)B(9)H(10)}(2)(&mgr;-P-P)] [P-P = dppe = 1,2-bis(diphenylphosphino)ethane (6), dppp = 1,3-bis(diphenylphosphino)propane (7)], where the dppe or dppp ligands bridge two gold nido-diphosphine units. The reaction of 1 with NaH leads to removal of one proton, and further reaction with [Au(PPh(3))(tht)]ClO(4) gives the novel metallocarborane compound [Au(2){(PPh(2))(2)C(2)B(9)H(9)}(PPh(3))(2)] (8). The structure of complexes 1 and 7 have been established by X-ray diffraction. [Au{(PPh(2))(2)C(2)B(9)H(10)}(PPh(3))] (1) (dichloromethane solvate) crystallizes in the monoclinic space group P2(1)/c, with a = 17.326(3) ?, b = 20.688(3) ?, c = 13.442(2) ?, beta = 104.710(12) degrees, Z = 4, and T = -100 degrees C. [Au(2){(PPh(2))(2)C(2)B(9)H(10)}(2)(&mgr;-dppp)] (7) (acetone solvate) is triclinic, space group P&onemacr;, a = 13.432(3) ?, b = 18.888(3) ?, c = 20.021(3) ?, alpha = 78.56(2) degrees, beta = 72.02(2) degrees, gamma = 73.31(2) degrees, Z = 2, and T = -100 degrees C. In both complexes the gold atom exhibits trigonal planar geometry with the 7,8-bis(diphenylphosphino)-7,8-dicarba-nido-undecaborate(1-) acting as a chelating ligand.     

Synthesis of new 6-substituted purinyl-5′-nor-1′-homocarbanucleosides based on indanol

A series of new 6-substituted purinyl-5′-nor-1′-homocarbanucleosides based on indanol were synthesized from (±)-cis-3-hydroxymethyl-1-indanol, an appropriately functionalized derivative of which was reacted with 6-chloropurine in the presence of NaH and 18-crown-6 ether to prepare a key intermediate that gave access to the target molecules, purinylcarbanucleosides in which position 6 is occupied by a chloro, hydroxy, methoxy, amino or substituted phenyl group.     

Isotopic scrambling in Di-13C-labeled 2-butyl cation: evidence for a protonated cyclopropane intermediate

The (13)C NMR spectrum of 2-butyl-1,2-(13)C(2) cation (1) is unchanged on heating the sample to -78 degrees C, indicating no isomerization to another isotopomer. In contrast, the spectrum of 2-butyl-2,3-(13)C(2) cation (2) shows rapid formation of all of the other isotopomers except 1. These results are consistent with a protonated cyclopropane intermediate in the rearrangement process. In this mechanism, either C(1) and C(2) or C(3) and C(4) interchange. Only the bond between C(2) and C(3) breaks.     

Acylaminoacetyl derivatives of active methylene compounds. 2. The cyclization of the acetylaminoacetyl derivatives to α-substituted tetramic acids and the formation of N-acetyl-α-substituted tetramic acids

The reaction of aceturic acid p-nitrophenyl ester with active methylene compounds Y-CH₂-CO₂R has been found to give either the normally expected C-acylation compounds 2 (Y = -CN, -CO₂R, -COCH₃) or N-acetyl-α-Y-substituted tetramic acids 3 (Y = -CO₂R,-COCH₃), depending on the reaction conditions. Moreover, the intramolecular condensation of the C-acylation compounds 2 derived from malonic and acetoacetic esters (Y = -CO₂R, -COCH₃) to α-Y-substituted tetramic acids is shown to proceed through initial cyclization to the corresponding N-acetyl-α-Y-substituted tetramic acids 3 (Y = -CO₂R, -COCH₃).     

Electrostatics of PEGylated micelles and liposomes containing charged and neutral lipopolymers

The electrostatics of large unilamellar vesicles (LUVs) of various lipid compositions were determined and correlated with steric stabilization. The compositional variables studied include (a) degree of saturation, comparing the unsaturated egg phosphatidylcholine (EPC) and the fully hydrogenated soy phosphatidylcholine (HSPC) as liposome-forming lipids; (b) the effect of 40 mol % cholesterol; (c) the effect of mole % of three methyl poly(ethylene glycol) (mPEG)-lipids (the negatively charged mPEG-distearoyl phosphoethanolamine (DSPE) and two uncharged lipopolymers, mPEG-distearoyl glycerol (DSG) and mPEG-oxycarbonyl-3-amino-1,2-propanediol distearoyl ester (DS)); and (d) the negatively charged phosphatidyl glycerol (PG). The lipid phases were as follows: liquid disordered (LD) for the EPC-containing LUV, solid ordered (SO) for the HSPC-containing LUV, and liquid ordered (LO) for either of those LUV with the addition of 40 mol % cholesterol. The LUV zeta potential and electrical surface potential (psi(0)) were determined. It was found that progressive addition of mPEG(2k)-DSPE to liposomes increases negative surface potential and reduces surface pH to a similar extent as the addition of PG. However, due to the "hidden charge effect", zeta potential was more negative for liposomes containing PG than for those containing mPEG(2k)-DSPE. Replacing mPEG-DSPE with mPEG(2k)-DS or mPEG-DSG had no effect on surface pH and surface potential, and zeta potential was approximately zero. Addition of low concentrations of cationic peptides (protamine sulfate and melittin) to PG- or mPEG-DSPE-containing liposomes neutralized the liposome negative surface potential to a similar extent. However, only in liposomes containing PG, did liposome aggregation occur. Replacing the negatively charged lipopolymer mPEG-DSPE with the neutral lipopolymers mPEG-DS or mPEG-DSG eliminates or reduces such interactions. The relevance of this effect to the liposome performance in vivo is discussed.     

A very large diversity space of synthetically accessible compounds for use with drug design programs

We have constructed a very large virtual diversity space containing more than 10¹³ chemical compounds. The diversity space is built from about 400 combinatorial libraries, which have been expanded by choosing sizeable collections of suitable R-groups that can be attached to each link point of their scaffolds. These R-group collections have been created by selecting reagents that have drug-like properties from catalogs of available chemicals. As members of known combinatorial libraries, the compounds in the diversity space are in general synthetically accessible and useful as potential drug leads. Hence, the diversity space can be used as a vast source of compounds by a de novo drug design program. For example, we have used such a program to generate inhibitors of HIV integrase enzyme that exhibited activity in the micromolar range.     

Understanding the conformational dependence of spin-spin coupling constants: through-bond and through-space J(31P,31P) coupling in tetraphosphane-1,4-diides [M(L)x]2[P4R4

The characteristic dependence of J(31P,31P) spin-spin coupling constants of alkali metal tetraphosphane-1,4-diides on structure and composition has been analyzed by density functional methods. The computations confirm that the structure of the contact ion pairs is conserved in solution. Calculations on model systems M2P4H4, on naked P4H4(2-) anions, and on models including point charges, show that the role of the cations is mainly structural and to a smaller extent electrostatic. Three of the four J(P,P) coupling constants depend characteristically on the conformation of the anion, which in turn is determined by the substituents R and by cation-anion interactions. Several couplings exhibit a large through-space component and are thus strongly dependent on the relative orientation of nonbonding electron pairs on the phosphorus atoms involved. This is shown by visualization of coupling pathways using the recently introduced coupling energy density (CED), in combination with the electron localization function (ELF).