Fluorescence enhancement of the Eu3+-tetracycline complex by DNA or RNA was studied. Studies involving natural and denatured fish sperm DNA, calf thymus DNA, and yeast RNA revealed that double-stranded and singlestranded DNA is capable of enhancing the fluorescence of the Eu3+-tetracycline complex, while RNA showed very little enhancement effect, which founded a basis for selective determination of DNA in the presence of RNA. Maximum fluorescence was produced in the pH range 8.0-9.7, with maximum excitation and emission wavelengths at 398 and 615 tun, respectively. Under optimal conditions, the calibration graphs were linear between 0.02 and 1.0 /zg mL-1 for both double-stranded calf thymus and fish sperm DNA. The corresponding detection limits were 0.01 /zg mL-1. The relative standard deviation (seven replicates) was within 3.0% in the linear range. DNA could be determined in the presence of yeast RNA. If the time-resolved mode was used, the low end of the linear range could be extended to 0.005 /zg mL-1, with a detection limit of 0.003 /zg mL-1, The mechanism for the fluorescence enhancement was also studied.Direct use of the fluorescence emission properties of nucleic acids to investigate their biological properties has been limited,1•1 2 whereas interest in trivalent lanthanide cations as fluorescence probes of the structure and function of nucleic acids has increased markedly.3 45™6 In particular, attention has been directed toward two rare earth cations, Tb3+ and Eu3+, as their resonance energy levels overlap with the triplet energy states of nucleic acid ligands irradiated with ultraviolet light.7 We previously reported the fluorescence enhancement of Tb3+ by nucleic acids and nucleotides in the presence of phenanthroline,8•9 but the nucleic acids (1)

Fourier transform infrared spectroscopic study of human breast normal and carcinomal tissues has been carried out. Some distinctive spectral differences which are mainly due to nucleic acids and proteins are observed between normal and carcinomal tissues. This method of analysis results in nearly 100% diagnostic accuracy of carcinomal tissues from normal tissues. The spectral patterns of well‐differentiated carcinomal tissues exhibit marked heterogeneity, however that of poorly differentiated carcinomas demonstrate significant similarity. Apocrine, tubular, intraductal and mucinous carcinomas and invasive infiltrating ductal carcinomal tissues can be discriminated based on their characteristic spectra. The spectral differences confirm the possibility of using FTIR as an accurate and rapid technique to distinguish between normal and malignant breast tissues and classify breast carcinomas in different subtypes.

A study of the enhancement of the fluorescence intensity of the Eulll -thenoyltrifluoroacetone (-A) -trioctylphosphine oxide (TOPO) system by Lalll, Gdlll, Lull1 and Ylll has been carried out in a colloidal-like suspension. Gadolinium(ll1) caused the largest enhancement of the fluorescence intensity. In the presence of this element the weak fluorescence of the Eulli-TTA -TOPO system was enhanced by a factor of about 18 at a pH of between 5.5 and 6.5. The excitation and emission wavelengths were 343 and 61 5 nm, respectively. The fluorescence intensity was linear up to 10-8 M of europium; the detection limit was found to be 5 x I O -I~M and the precision at 8.0 x 1 0 -1 1~ of europium was 1.4%. By stabilising the fluorescence with cetyltrimethylammonium bromide (CTAB), the Eulll -TTA -TOPO -Gd"1 system together with three other enhancing systems could be applied to the determination of trace amounts of europium in lanthanide oxides and yttrium oxide. The fluorescence intensity of the Srnlll -TTA -TOPO system was also enhanced by La"1, Gdlll, Lull1 and Ylll. The factors influencing the fluorescence enhancement are discussed and a general mechanism involving an intermolecular transfer of energy from the enhancing complex to the fluorescing complex is proposed.In solution, the ternary complexes formed by the reaction of europium or samarium with thenoyltrifluoroacetone (TTA) and certain substituted ammonium cations or neutral ligands, such as nitrogen and phosphorus oxides (L), will usually emit an intrinsic fluorescence for the metal ion when exposed to ultraviolet radiation.'-3 However, the fluorescence is seriously interfered with by other lanthanide ions and europium and samarium mutually interfere. In the past, the solvent extraction method was commonly employed for the elimination of interferences, whereas nowadays an organic solvent or a surfactant is added to the system in order to increase selectivity and sensitivity."-7 Compared with the solvent extraction method, the latter procedure is a simple and efficient means of improving the fluorimetric determination of europium and samarium. Over the last few years interest in the application of micellar systems has increased. So far, the micellar-enhanced fluorimetric method seems to be the only type of enhanced fluorimetric method available for the determination of trace amounts of lanthanide ions.Recently, it has been shown that some of the lanthanides, yttrium and the alkaline earth metal ions can enhance the intrinsic fluorescence of a lanthanide comp1ex.x-1" For example, the sensitivity and selectivity of the Eu"' -TTA -L and Sm"1 -TTA -L systems were increased by the addition of trivalent lanthanum, gadolinium, lutetium or yttrium ions; in all instances Gd"' caused the largest enhancement of the fluorescence intensity. Early in 1967, during a study of the fluorescence characteristics of the ion associate of Eu"I (or SmIrr) with TTA -H-collidine, Melenteva et al. I 1 observed that the fluorescence intensity of the system was enhanced dramatically by the addi...

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