Lanthanide complexes exhibit interesting spectroscopic properties yielding many applications as imaging probes, natural chirality amplifiers, and therapeutic agents. However, many properties are not fully understood yet. Therefore, we applied magnetic circular dichroism (MCD) spectroscopy, which provides enhanced information about the underlying electronic structure to a series of lanthanide compounds. The metals in the M(3+) state included Y, La, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu; the spectra were collected for selected tetraphenylporphin (TPP) and octaethylporphin (OEP) complexes in chloroform. While the MCD and UV-VIS absorption spectra were dominated by the porphyrin signal, metal binding significantly modulated them. MCD spectroscopy was found to be better suited to discriminate between various species than absorption spectroscopy alone. The main features and trends in the lanthanide series observed in MCD and absorption spectra of the complexes could be interpreted at the Density Functional Theory (DFT) level, with effective core potentials on metal nuclei. The sum over state (SOS) method was used for simulation of the MCD intensities. The combination of the spectroscopy and quantum-chemical computations is important for understanding the interactions of the metals with the organic compounds.

We examined changes in nucleic acids and concomitant population development of the copepods Acartia bifilosa and Eurytemora affinis in relation to the progress of the phytoplankton spring bloom in the northern Baltic proper. Individual RNA and DNA concentrations and their ratios in female copepods as well as copepod abundance and population structure were analyzed in 2 coastal areas that differed in the degree of eutrophication and phytoplankton development. During the study period (February to June 2002), bloom conditions were evident, with chlorophyll (chl) a values being 42% higher in the eutrophic area than in the reference area. In both areas, diatoms dominated; in the reference area, they were replaced by dinoflagellates toward the end of the bloom. Copepod RNA-DNA concentrations increased rapidly at the onset of the bloom and gradually decreased thereafter. Moreover, in the eutrophic area, both copepods had higher RNA content and RNA:DNA ratios throughout the study period, suggesting higher productivity in this area. In both species, we found positive correlations between RNA-based indices and chl a. Thus, as suggested by RNA dynamics, growth rates of A. bifilosa and E. affinis appear to respond rapidly to both temporal variation in spring phytoplankton stock and spatial variation due to the magnitude of the bloom. In addition, we found that species-specific RNA dynamics and RNA−chl a relationships differed between species, indicating possible differences in feeding preferences and growth potential. KEY WORDS: Biochemical indices · Growth conditions · Population development · RNA and DNA content · Spring phytoplankton bloom Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 349: [213][214][215][216][217][218][219][220][221][222][223][224][225] 2007 of fish stock recruitment (Parmanne & Sjoeblom 1988). Therefore, the magnitude and timing of copepod reproduction during spring may affect the Baltic ecosystem and its commercial fisheries. However, while a wealth of information can be found on copepod population dynamics and the physiological status associated with phytoplankton blooms in the North Atlantic, there are only a few studies on this aspect in the Baltic Sea.To assay the response of copepods to the onset of a phytoplankton bloom, egg production rate measurements (e.g. Dam et al. 1994, Ward & Shreeve 1995, gonad development staging (Niehoff et al. 2002), feeding rate estimates (Dam et al. 1994, Atkinson et al. 1996, and metabolic indices (Hernandez-Leon et al. 2004) have been employed. Nucleic acid content has also been used to assess copepod nutritional conditions during bloom periods (Durbin et al. 2003), providing in situ estimates of copepod growth status. The rationale of using nucleic acid quantities as a growth measure is that total RNA content in a somatic cell is primarily a function of ribosome number correlating with protein synthesis, while the amount of DNA is quasi-constant and may therefore be an index of the cell number (Buckle...

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