Tetra-pyrrole

Most of the resorbed iron serves for the formation of red blood cells in the bone marrow (erythropoiesis, top). As discussed on p. 192, it is only in the final step of hem biosynthesis that Fe "" is incorporated by ferro-chelatase into the previously prepared tetra-pyrrol framework. 

Fig. 1 Basic structure (left side) and the absorption spectra (right side) of some photosensitizers. The absorption spectra of porphyrins (derived from porphins) consists of a Soret band (around 400 nm) and four Q-bands. Upon reduction of one or two double-bonds of the tetra-pyrrole structure or by expanding the number of 7i-electrons (by expanding the ring structure), the outermost Q-band becomes bathochromically shifted and the absorption coefficient increased as indicated on the figure. As described in the text, such chemical modifications are important for improving the therapeutic effect in deeper tissue layers...

Supramolecular metallocomplex systems on the basis of crown-substituted tetra-pyrroles 04UK6. 

G26. Greenberg, D. M., ed., Metabolic Pathways. Vol. 3. Amino Acids and Tetra-pyrroles, 3rd Ed. Academic Press, New York, 1969. 

Cytochromes are versatile, electron-transfer proteins containing a heme, i.e., a macrocyclic tetra-pyrrole coordinated to an iron atom, as the prosthetic group, similar to that found in hemoglohin and myoglohin. According to their characteristic absorption spectra and chemical composition, cytochromes may he divided into three groups, namely, cytochromes-a, -b and -c. Cytochromes transfer electrons with a change in the oxidation state between Fe (III) and Fe (II) in the heme. 

Fig. 5. Comparison of the 71-system conjugation (delocalization) in various biological tetra-pyrroles, as originally pointed out by Eschenmoser [90]. Heavy lines indicate the 7T-system in each tetrapyrrole. Reproduced, with kind permission, from Reference [10], 1991, by Elsevier Science - NL, Sara Burgerhartstraat 25,1055 KV Amsterdam, The Netherlands...

We first offer a few qualitative observations concerning core conformations in tetra-pyrrole derivatives. As is generally known, the 24-atom core is readily deformed in a direction perpendicular to the mean plane, but less so in the radial (in plane) direction. Further, the pyrrole ring subunits are always planar. The first observation is a very... 

The story starts some fourteen years after Baeyer had initiated the first study of phenol-formaldehyde condensation chemistry (which led to the study of phenol-formaldehyde resins and subsequently to calixarene chemistry)" - with the publication of his paper on the condensation of pyrrole and acetone. Baeyer mixed pyrrole, acetone and hydrochloric acid and obtained a white crystalline material, which later proved to be the tetra-pyrrolic macrocycle, me.so-octamethylcalixpyrrole 1. 

Granick, 8., and Gilder, H. 1947. Distribution, structure and properties of the tetra-pyrroles. Advances in Emymology 7, 305. 

Conversion of Haemoglobin Pigment into Bilirubin.—I mberg has shown that oxidation of a haemochromogen opens up the tetra-pyrrole ring to form a green verdohaemochromogen, v/hich is a linear tetrapyrrole and convertible into biliverdin by removal... 

In reaction centers (RC) of Rhodobacter spheroides (Rb.), the tetra-pyrrole pigments at the sites B ("monomeric" bacteriochlorophylls,... 

Phycoeryth rin Rhodophyta Linear tetra pyrrole Molecular biology (ELISA, flow cytometry) 128/1 mg... 

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