Interaction of the photosystem 1 reaction center with antenna chlorophyll in a pigment-protein complex isolated from pea chloroplasts

Using a specially developed phosporoscopic attachment to spectropolarimeter, light induced spectra of circular dichroism (CD) in region 600-750 nm were measured for a pigment protein complex of photosystem 1 (PC-1) isolated from pea chloroplast (chlorophyll : P700 = 40). Minor components at 672 and 678 nm are observed in light induced spectra besides the components of dimer splitting of P700 Qy transition at 691 and 698 nm. Haussian deconvolution of light induced CD spectra of P700 and low temperature CD spectrum of PC-1 indicates that minor components are due to forms of antenna chlorophylls Chl672 and Chl678, rotational strength of that is changed by 2-4% as a result of P700 oxidation. Long term incubation of PC-1 with Triton X-100 inhibits P700 and destroys longwave optically active chlorophyll forms. A strong relation between dichroic density of 693 nm band in CD spectrum of PC-1 and the value of light induced absorption change at 698 nm could be used to determine P700 concentration on the basis of CD spectrum of PC-1. Such a relation shows that Chl693 is an important component of photo-system 1 reaction center. It is suggested that P700 is not an isolated dimer but it is included in the local complex from 8-10 chlorophyll molecules (Chl672, Chl678, Chl686, Chl693).     

Bacteriochlorophyll fluorescence changes related to the bacteriopheophytin photoreduction in the chromatophores of purple sulfur bacteria]

It is shown that illumination of chromatophores of sulfur bacterium Chromatium minutissimum at Eh of the medium --200 mV divided by --620 mV (when the photooxidation of pigment P890 is completely inhibited) induces a decrease in bacteriochlorophyll fluorescence yield, reversible in the dark. Under these conditions a reversible photoreduction of bacteriopheophytin is detected (bleaching of absorption bands at 543 and 760 nm and development of a band at 650 nm), which is accompanied by a blue shift of the absorption band at 8 nm. As a possible interpretation of these effects the suggestion is made on the function of bacteriopheophytin as a primary electron acceptor in reaction centers of bacteria. The bacteriopheophytin photoreduction, followed by a decrease in fluorescence yield, is also observed in other sulfur bacteria, Thiocapsa roseopersicina and Ectothiorodospira shaposhnikovii, but it is not detected in nonsulfur bacteria, Rhodospirillum rubrum and Rhodopseudomonas spheroides. This is considered as an evidence for the difference in the functional organization of the reaction centers of these two groups of bacteria,     

Genetic engineering of peptide hormones. I. Cloning and primary structure of cDNA of chicken growth hormone

The cDNA coding for the chicken growth hormone was cloned and sequenced. The 795 base pairs long cDNA insert contains a 5'-untranslated region (35 b.p.), a sequence coding for precursor of growth hormone (648 b.p.), a 3'-untranslated region (96 b.p.) and a poly(A)-tail (16 b.p.). Comparison of the cDNA sequence cloned by us with that published earlier revealed several differences including the additional unique HinfI site at the position corresponding to codons for Leu-87 and Thr-88.     

Changes in the circular dichroism spectra and melting parameters of complexes of histones with DNA of different GC-composition

It was shown that there existed a correlative connection between total clip activity and circular dichroism relative ellipticity. It is supposed that the parameters of total clip activity also may carry information about DNA conformation in the complexes with histones.     

Theory of Helix-Coil Transition on DNA-Ligand Complexes: The Effect to Two Types of Interaction of Ligand on the Parameters of Transition

Abstract

The effect of ligand interacting with native DNA by two types on the parameters of helix-coil transition in homopolymers is considered using the most probable distribution method (Yu.S. Lazurkin et al., Biopolymers 1970). It is shown that at a small relative concentration of ligand the melting enthalpy (ΔH) of DNA may be obtained from the universal formula which contains only values directly known from the experiments. It is shown that the formula for the change of melting temperature and width of melting range depending on the total ligand concentration in solution is converted into the corresponding formulae which are defined for the case when only one type of interaction of ligand and DNA is considered.     

Interrelation of the sensitivity of Salmonella derby cells to phage dp8 with the R plasmid of Salmonella derby

In the process of studying phage--Salmonella derby plasmid interaction effect, it has been found that the absence of the plasmid blocks the adsorption step and the step of phage penetration into the cell. However, the lytic functions and those responsible in maintenance of the lysogenic state are independent of plasmid. Probably, resistance of plasmidless cells of S. derby to extracellular dp8 phage is mediated by the absence of plasmid-borne genes in S. derby coding for membrane peptides which are indispensible for adsorption and DNA penetration into the cell.