Surfactant displacement of human serum albumin adsorbed on loosely packed self-assembled monolayers: cetyltrimethylammonium bromide versus sodium dodecyl sulfate

The surfactants sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) displace human serum albumin (HSA) from loosely packed self-assembled monolayers (SAM) of hydrophobic alkyl chains by different means. Removal of HSA is of interest because previous work has suggested that the adsorption of HSA to such loosely packed SAMs may be sufficiently tenacious to offer opportunities for surface passivation. While HSA remains on the surface after exposure to SDS and rinsing, no protein remains after exposure to CTAB and rinsing. X-ray reflectivity and X-ray photoelectron spectroscopy measurements indicate that CTAB molecules remain interdigitated in the loosely packed SAM after rinsing, suggesting that CTAB is more effective in removing the HSA because it interacts more strongly with the SAM.     

Reactions of metal carbonyl cluster complexes with multidentate phosphine ligands; reactions with bis(diphenylphosphino)methane

Reactions of Rh₆(CO)₁₆ with bis(diphenylphosphino)methane (dppm) gave Rh₆(CO)₁₄(dppm), Rh₆(CO)₁₂(dppm)₂, or Rh₆(CO)₁₀(dppm)₃, depending upon the reaction conditions. Rh₄(CO)₁₀(dppm) may be obtained from the reaction of Rh₄(CO)₁₂ with dppm, but this derivative rapidly decomposes in solution to give Rh₄(CO)₈(dppm)₂, Rh₆(CO)₁₄(dppm), and Rh₆(CO)₁₂(dppm)₂. Ir₄(CO)₁₀(dppm) and Ir₄(CO)₈(dppm)₂ have also been prepared, and their structures are discussed on the basis of infrared and ³¹P NMR spectroscopic data.     

Reduced inorganic phosphorus in the natural environment: significance, speciation and determination

It is commonly assumed that phosphorus occurs almost exclusively in the environment as fully oxidized phosphate (primarily H₂PO₄⁻ and HPO₄²⁻, where the oxidation state of phosphorus is +V). Recent developments in the field of microbiology and research on the origin of life have suggested a possibly significant role for reduced, inorganic forms of phosphorus in bacterial metabolism and as evolutionary precursors of biological phosphate compounds. Reduced inorganic forms of phosphorus include phosphorus acid (H₃PO₃, P(+III)), hypophosphorus acid (H₃PO₂, P(+I)) and various forms of phosphides (P(−III)). Reduced phosphorus has been detected in anaerobic sediments, sewage treatment facilities and in industrial and agricultural processes.Microbiological evidence suggests a significant role for reduced phosphorus species in metabolic processes and raises interesting questions regarding the biogeochemistry of this nutrient in the environment. However, the paucity of data on the presence and cycling of reduced phosphorus compounds in the environment requires attention in order to elucidate the role of these compounds in natural systems. This paper discusses the significance of reduced phosphorus in the natural environment, its speciation and methods of detection.     

The effect of the t-butyl substituent on polymer properties in homopolymer systems

The effect of a bulky substituent on properties of different homopolymers has been examined. The substituent is the t-butyl moiety attached to a benzene ring found in the repeat units of the homopolymers of polyesters, polyarylates, polyamides, and polyaramides. These polymers have been prepared by melt, solution, or interfacial techniques. The source of the t-butyl group is mainly from 5-t-butylisophthalic acid (5TBIA) and comparisons are generally made with corresponding homopolymers based on isophthalic acid. The effect of the t-butyl group is shown by comparison of the properties of these homopolymers. Thermal and mechanical (tensile and impact) properties, density, water absorption, solubility, and processability are discussed. Differences in these properties are attributed to the t-butyl group and are based on intermolecular and intramolecular interactions that include increased free volume, chain stiffening, and conformational changes.     

Determination of copper in medicinal plants used as dietary supplements by atomic absorption spectrometry with direct flame solid analysis

An alternative device for the direct solid analysis (DSA) for copper determination by flame atomic absorption spectrometry (FAAS) is proposed. Copper was directly determined in commercial medicinal plants used as dietary supplements. The determination of copper in solid samples by DSA–FAAS was made by using a conventional air–acetylene flame. Between 0.05 and 1.5 mg of each test, sample was weighed directly into a small polyethylene vial connected to the device used for solid introduction into the flame. Test samples were introduced into the flame as a dry aerosol using a T-quartz cell set between the burner and the optical path. The T-quartz cell has a slit in the superior part by which the solid aerosol passes to the flame. A transient signal, evaluated as integrated absorbance, is produced and it is totally integrated in 2 s. Background signals always presented absorbance values less than 0.1. It was found a characteristic mass of 0.8 ng Cu and absolute limit of detection of 1.2 ng (3 s), or 1.2 μg g⁻¹ if a sample mass of 1 mg was used. Optimized conditions for air flow rate, flame stoichiometry, and so on were established as well. No excessive grinding of the samples was needed and samples with particle of size less than 80 μm were used throughout. No statistical difference between the results from the proposed system and those obtained by sample digestion and determination by conventional FAAS was observed. With the proposed procedure, more than 50 test samples can be analyzed in 1 h and it can be easily adapted to conventional spectrometers for FAAS.     

EFFICACY OF PHOTODYNAMIC THERAPY ON ORIGINAL AND RECURRENT RAT MAMMARY TUMORS

Abstract— Photodynamic therapy has demonstrated efficacy toward primary, metastatic and recurrent human tumors. Here, we investigated the ability of photodynamic therapy, using Photofrin, to inhibit growth of R3230AC mammary adenocarcinomas when tumors were treated as original implants and again as lesions recurring at the initial treatment site. The results demonstrate that both initial implants and lesions recurring after the first photodynamic treatment respond similarly to the same photodynamic therapy protocol, with mean tumor volume doubling times of ˜ 11 days in both cases. Cells cultured from original tumor implants or tumors that recurred after photodynamic treatment accumulate equivalent amounts of [¹⁴C]polyhematoporphyrin. Single cell suspensions prepared from either original or recurrent tumors from animals administered 5 mg/kg Photofrin and exposed to light in vitro displayed comparable phototoxicity. Additionally, examination of tumors by light microscopy revealed no morphological differences between the original tumor implants and the recurrent lesions. Taken together, these data indicate that lesions which recurred at the site of the initial photodynamic treatment were not resistant to a second identical course of photodynamic therapy.     

Aspects of stereochemistry—I Properties and reactions of some diols

The extent of intramolecular hydrogen-bonding, as determined by infra-red spectroscopy in the hydroxyl stretching region, in certain vicinal diols of cyclohexane, cyclopentane, tetrahydropyran and tetrahydrofuran and in related compounds provides evidence for the stabilities of different conformations. In certain compounds these stabilities can be affected by hydrogen bonding from a substituent hydroxyl group to a ring oxygen. Additional evidence is provided in the case of the tetrahydropyran diols by [M]_D values. The rate of reaction of the vicinal diols of these cyclic systems with glycol splitting reagents, and their zone electrophoretic mobility in an alkaline borate buffer is influenced by the presence of a ring oxygen.