THE CHEMILUMINESCENCE OF AMIDES AND MONOACYL HYDRAZIDES BASED ON FIREFLY DEHYDROLUCIFERIN

Monoacyl hydrazides based on 5-methyldehydroluciferin and simpler analogs have been synthesized; they proved to be chemiluminescent on treatment with a strong base in DMSO in the presence of oxygen. The light emitters in these cases appear to be the corresponding carboxylate ions; a pathway involving an oxidative decarboxylation was eliminated as a possibility by consideration of the fluorescence wavelengths of the corresponding oxyluciferins. A reaction mechanism for the luminescence involving the possible intermediacy of an azadioxetane is proposed. The corresponding amides were also synthesized; they proved to be equally chemiluminescent to the hydrazides in the dehydroluciferin series.     

On inversion of linear descriptor-variable control systems containing input derivatives

Linear control systems of the form E = Ax + Bv, y = Cx + Dv,are considered, where v is a column composed of the controlu and its first k derivatives, and E is a singular square matrix.This problem is this: find a system R = Fz + Gw, Lv = Hz + Jw,where w is some linear combination of y (the output of the originalsystem) and its derivatives. For the solution of this problem,a method (based on the use of matrix generalized inverse) isdeveloped that can be applied both to time-invariant and totime-varying systems. For the time-invariant case, a numericalprocedure is presented that either yields a system of the desiredform in which the coefficient matrices are of the smallest possibledimensions or shows that there is no such system.     

THE FATE OF PYRIMIDINE DIMERS IN ULTRAVIOLET-IRRADIATED CHLAMYDOMONAS

Abstract— We have developed a chromatographic technique for the separation of ³²P-labeled pyrimidine nucleotide dimers of the form Py_pPy from ³²P-phosphate in enzymatic hydroly sates of ultraviolet-irradiated DNA. Application of this technique to ³²P-labeled Chlamydomonas reinhardii shows that ultraviolet irradiation of this organism induces pyrimidine dimers in both nuclear and chloroplast DNA. We have found no evidence that these dimers are excised from either DNA species after several hours incubation under non-photoreactivating conditions. A function has been derived to permit the pyrimidine-dimer content determined from radioactive-thymine-labeled cells to be conveniently compared to that obtained from ³²P-phosphate-labeled cells.     

PHOTOPHYSICAL AND PHOTOBIOLOGICAL PROPERTIES OF DIPORPHYRIN ETHERS

Spectral properties of several diporphyrin ethers were assessed in different solvents and after accumulation by leukemia L1210 cells in vitro. To facilitate studies in a variety of solvents, both tetramethylesters of the diporphyrin ethers and free acids were employed. For comparison, studies on the corresponding porphyrin monomers were also carried out. The joining of two porphyrins by an ether linkage had several consequences. We observed a blue shift in the Soret band of the ethers, but not of the corresponding simple porphyrins, in protic solvents. This phenomenon is likely related to ether aggregation under conditions which promote H-bonding. The presence of an ether linkage was associated with enhanced fluorescence at 630-640 nm and decreased fluorescence lifetimes and yields, especially in protic solvents. The ether linkage was unaffected by intracellular enzymes, but porphyrin esters were readily hydrolyzed upon accumulation by L1210 cells. The joining of two hematoporphyrin molecules by an ether linkage promoted dye accumulation by L1210 cells. In contrast, accumulation of mesoporphyrin and protoporphyrin was thereby retarded.     

STUDIES ON SOME INTERMEDIATES AND PRODUCTS OF THE PHOTOREDUCTION OF 9,10-ANTHRAQUINONE *,†

Abstract— The mechanism of the photoreduction of 9,10-anthraquinone (AQ) in alcohol and hexane has been studied by flash photolysis. The fluorescence spectrum of the photoproduct, 9,10-dihydroxy anthracene shows a large shift between hexane and ethanol. The quantum yields of photoreduction for AQ are solvent-dependent, the reaction between the solvent radical and AQ determining the quantum yield.
The absorption spectrum of the 9,10-anthrasemiquinone (AQH.) has a long-wavelength absorption band with peaks at 631 and 678 nm. The second-order decay constants for AQH. were estimated to be 1.3 × 10⁹, 6.7 × 10⁸ and 2.0 × 10⁸ M ^-1 sec^-1 in ethanol, 2-propanol and ethylene glycol, respectively.
A long-wavelength absorption band was observed for 9,10-anthrasemiquinone radical anion, having peaks at 776 and 860 nm; epsi;_max= 1900 at 776 nm. This spectrum is compared with the spectra of 9,10-dihydroxy anthracene mono- and di-anions. The 9,10-anthrasemiquinone radical anion was found to photoreduce quantitatively to 9,10-dihydroxy anthracene mono-anion with a quantum yield of 0.1.     

PHOTOSENSITIZATION WITH DERIVATIVES OF CHLOROPHYLL

The properties of several chlorophyll derivatives were examined: the methyl esters of pheophorbide A, pheophorbide B and pheophytin. In spite of structural differences, all products were equally effective sensitizers in vitro and were localized equally well by murine tumors in vivo after 1 h. But only the pheophytins persisted at neoplastic loci for 24 h. There was no evidence of hydrolysis of the methyl esters, but the phytyl ester linkage was labile in vivo.     

A discrete Galerkin method for a hyperslngular boundary integral equation

Received on 14 August 1995. Revised on 20 August 1996. Consider solving the interior Neumann problem with D a simply-connected planar region and S=D a smooth curve.A double-layer potential is used to represent the solution,and it leads to the problem of solving a hypersingular integralequation. This integral equation is reformulated as a Cauchysingular integral equation. A discrete Galerkin method withtrigonometric polynomials is then given for its solution. Anerror analysis is given, and numerical examples complete thepaper.     

AN INDIVIDUAL-BASED FISHERY MODEL AND ASSESSING FISHERY STABILITY

ABSTRACT. The stability of a fishery system was investigated using two forms of a stochastic computer simulation model that was individually based in terms of the fishing boats. Fish catch was partitioned among boats according to two catch processes: an unranked process in which all boats had equal ability to catch fish and a ranked catch model in which a boat's ability to catch fish depended on its wealth. Stock size, total catch, fleet size and individual boat wealth were modeled over a series of years. In the unranked catch model the fish stock size and fleet size were significantly more variable than in the ranked catch model.     

Stellar dynamics and black holes

Chandrasekhar’s most important contribution to stellar dynamics was the concept of dynamical friction. I briefly review that work, then discuss some implications of Chandrasekhar’s theory of gravitational encounters for motion in galactic nuclei.