Mehrnaz Katouzian-Safadi

Photochemical cross-linking of the cyclic adenosine 3',5' monophosphate receptor protein to Escherichia coli 5-bromouracil-substituted DNA. Role of the effectors

Abstract— Cyclic AMP receptor protein (CRP) is a regulatory protein implicated in the transcription of several operons in Escherichia coli. Its activity is modulated by effectors, such as cAMP or cGMP, which could induce (or not) structural changes in the protein, and activate (or not) the transcription. CRP can bind non‐specifically to DNA, and we investigated the photocross‐linking of the protein to E. coli 5‐bromouracil‐substituted DNA, in the absence and in the presence of effectors. The photochemistry of the protein alone, under the conditions used for the cross‐linking reaction, was studied. We show that tryptophyl residues are more photoreactive than tyrosyl ones. Photocross‐linking of the protein implicates only one of the two subunits, and the rate of the reaction is not modified upon cAMP binding. Binding of cGMP reduces the rate of photocross‐linking by a factor of two. These new results show that the protein in the CRP‐cGMP complex behaves differently from the free protein.

Identification of the DNA-interacting sites of proteins: Microsequencing of the peptides cross-linked to 5-bromouracil substituted DNA

Photochemical induced cross-links between protein and nucleic acids are useful tools in the study of the protein-DNA interactions. The substitution of thymine by 5-bromouracil in DNA increases the photocross-linking yield, and reduces the direct damages to both DNA and proteins. Using the lac repressor-DNA non-specific interaction system, we have developed a procedure to identify the interaction site on the protein. Sensitive, accurate and inexpensive in time and material, this procedure is based on the possibility of sequencing peptides in the presence of a large excess of DNA. The obtained result (the implication of His 29) agrees with previous work.

Studies on the Phenomenon of Turnip Yellow Mosaic Virus RNA Release by Freezing and Thawing

Summary In particles of turnip yellow mosaic virus (TYMV), the interactions between proteins are particularly strong when compared to those between proteins in some other icosahedral viruses. Intact RNA is released from TYMV particles on freezing and this process has been studied by examining several parameters that influence cryodenaturation such as dehydration, pressure, aggregation and the presence of protective agents (glycerol and ammonium sulphate). Pressure of 1.5 × 108 Pa had no effect on virus particles whereas dehydration of a virus suspension had a drastic effect. Aggregate formation resulting from freezing of solutions containing high virus concentrations seems to be a prerequisite for RNA release; cryoprotective agents hindered RNA release.

Clays and Health

First book in English which describes the pharmaceutical and therapeutic benefits of clays in terms of their physical and physicochemical properties. Provides a concise history of the use of clay in human health practices. Unlike popular texts, this book describes the customary applications of clays and explains the mode of action causing the palliative effect

General Information on Clay Applications for Health and Well-Being

This chapter reports on the ordinary clay applications in the field of health: first, the function of the nature of the pathologies to be treated, second, the function of the clay potentialities to treat certain pathologies, and third, the function of the principal reactivity domains pertaining to clay and living organisms.

Historical Aspects of a Natural Pharmacopeia: Clay in the Corpus of The Medieval Pharmacopeia Written in Arabic

This chapter opens with an historical presentation of some translations of Ancient Greek medical texts. They reached us partly thanks to translations into Arabic carried out during the Middle Ages. These texts were progressively enriched and thereafter evolved autonomously. Stories of conquests and religions, both ancient and medieval, are superimposed on the evolution of this knowledge, without being the exclusive causes. Therapies based on clay and its various daily uses are described in the corpus of profane texts of pharmacy, pharmacopeia, medicine, and rules for healthy living. In this chapter these points, disclosed in chronological order and by topics, are dealt with, concentrated only on some fundamental studies in medicine and pharmacy.

Principal Modes of Clay Use

There is a long tradition of the use of clay for therapeutic purposes. The so-called healing or curative clay can be used either for internal or external applications. The so-called edible clay is a type of healing clay used for internal applications, ingested in the form of clay/potable water dispersions (argillic water), bits/pieces of natural clay, or even manufactured cookies or wafers consisting of a clay–animal fat blend and slowly chewed.

Therapies Based on Clay

The therapies based on clay dealt with in this chapter are classified in two main groups, physical therapies and chemical therapies, involving either physical or chemical exchanges between the clay- bearing material and the human body, respectively. Physical therapies involve energy exchanges that can be induced during a massage by employing mechanical pressure on the previously heated (maximum at 45–50°C) clay pack, and from the pressure and heat being applied; the beneficial effects of improvement of muscular tone and blood circulation through abrasive and gumming action may occur. Chemical therapies involve chemical exchanges that could be promoted and developed by the applied pressure and heat. Beneficial effects could result from the chemical exchanges of the transdermal absorption of eventual bioessential elements and compounds existing in the liquid phase.

Clay Reactivity Depending Upon the Crystallochemical Properties of Clay Minerals

The crystallochemical models of clay mineral structures are described in this chapter because clay properties and inherent reactivity depend entirely on the specificities of those structures. Clay reactivity is strongly conditioned by the surface properties of clay mineral particles that are basically dependent on the particle global electric charge and its spatial distribution pattern, different from basal surfaces to edge surfaces. Particle electric charge results mainly from atomic substitutions that occur in both the octahedral and tetrahedral layers. In clay minerals bearing interlayer spaces chemical reactivity also possibly occurs on internal surfaces.

Provisioning, Recycling, and Trade of Clay

Natural clay to be used in the field of health and well-being, whether used as it occurs at its natural site, or after extraction from the deposit, is submitted to a refining processing in order to concentrate the finest grain fraction (enriched in clay minerals sometimes associated with organic compounds and finely grained carbonates, potentially the most interesting components in therapeutic or cosmetic terms). In the first situation clay in the form of paste (after being mixed with mineral water, e.g., seawater) is used at its natural site or at a nearby site as mud in mud therapy treatments, or as small pieces chewed and ingested, or even ingested after being dispersed preferentially in potable water providing argillic water. Processed clay is available on the market in two main states: powders (used in pharmaceutical formulations) and paste (used in peloids to be applied, for instance, at spa resorts after undergoing more or less complex manipulation and maturation), and in both states a microbiological check-up is necessary to assure sanitary safety. This sanitary safety is also required when recycling previously used clay paste.