The triplet state of photosynthetic pigments has been widely used in the past as an internal nonde­ structive probe for the geometric and electronic structure of the pigment-protein complexes of photo­ synthetic bacteria. Especially the reaction center complex (RC) has been intensively studied by means of ESR in high field and zero field [1—7]. Less is known about antenna complexes. So far only...

Stark spectra for nonoriented molecules with typical broad inhomogeneous line widths are obtained by applying an ac electric field and detecting the change in absorbance at the second harmonic of the field modulation frequency. The analysis of such data in terms of molecular parameters such as changes in dipole moment and polarizability is often difficult. We outline a new method, called higher...

Greenberg, R. G. (1952). J. Amer. chem. Soc. 74, 6307. Kirkland, R. J. A. & Turner, J. F. (1959). Biochem. J. 72, 716. Kurahashi, K., Pennington, R. J. & Utter, M. F. (1957). J. biol. Chem. 228, 1059. Lagerkvist, U. (1955). Acta chem. 8cand. 9, 1028. Lagerkvist, U. (1958). J. biol. Chem. 233, 138. Lieberman, I. (1956). J. biol. Chem. 223, 327. Lineweaver, H. & Burk, D. (1934). J. Amer. chem. So...

When bleached, aerobically grown cells of Rhodopseudornonas spheroides are transferred to semi-aerobic conditions to induce bacteriochlorophyll synthesis, a new fluorescence band, with a maximum at 790 nm, is observed in addition to the 885 nm emission maximum normally seen in pigmented cells. The 790 nm fluorescence may be due to bacteriochlorophyll which has not been bound into the chromatoph...

PROSPECT, a widely-used leaf directional-hemispherical reflectance and transmittance model, currently treats the behaviour of chlorophylls a, b, carotenoids, and anthocyanins uniformly, leading to errors. A finer discrimination among these pigments in lightabsorbing plant tissues should improve the model. In this paper, a new calibration and validation phase of PROSPECT is performed using two c...

The abundance of life on Earth is almost entirely due to biological photosynthesis, which depends on light energy. The source of light in natural habitats has heretofore been thought to be the sun, thus restricting photosynthesis to solar photic environments on the surface of the Earth. If photosynthesis could take place in geothermally illuminated environments, it would increase the diversity ...

The accuracy of models for primary production and light propagation depends on correct assignment of absorption to photosynthetic pigments. The phytoplankton absorption coefficient is comprised of two components: photosynthetic and photoprotective absorption coefficients. A method based on the fluorescent excitation of chlorophyll a is used to quantify the photosynthetic absorption coefficient ...