Recombination of fragmented proteins

Directed evolution is a powerful method for generating novel molecules with desirable properties. In developing a new sensor to screen for protein-protein interactions, Tafelmeyer et al. report a clever strategy to evolve heterodimeric "split proteins" from a monomer in this issue of Chemistry & Biology.     

Recombination of hydrogen and oxygen in the technical gaseous waste of nuclear power plants

The recombination of hydrogen and oxygen in technical gaseous waste of nuclear power plants in enlarged scale experiment has been studied on the basis of our previous work.¹ The catalyst and its best operating conditions for recombination of hydrogen and oxygen determined in a small scale experiment were demonstrated and tested. The results show that the data obtained in an enlarged scale experiment agreed well with that of in a small scale test. The recombination rate of H₂ and O₂ was higher than 98.3% and 99.98% respectively. After recombination, the residual concentrations of H₂ and O₂ in waste gas were O₂<3 ppm, H₂<400 ppm. The Pd-Al₂O₃ catalyst and operating conditions determined for gaseous waste processing of nuclear power plants were satisfactory.     

Using the telobox to search for plant telomere binding proteins

Telobox is a Myb-related DNA-binding domain which is present in a number of yeast, plant and animal proteins. Its capacity to bind preferentially double-stranded telomeric DNA has been used in numerous studies to search for candidate telomeric proteins in various organisms, including plants. Here we provide an overview of these studies with a special emphasis on plants, where a specific subfamily of the proteins possessing the N-terminally positioned telobox is present in addition to more common C-terminal telobox proteins. We further demonstrate the presence of a telobox protein (CpTBP1) in Cestrum parqui, a plant lacking typical telomeres and telomerase. The protein shows nuclear localisation and association with chromatin. The role of this protein in ancestral and current telomere structure is discussed in the evolutionary context. Altogether, the present overview shows the importance of the telobox domain in a search for candidate telomere proteins but at the same time warns against oversimplified identification of any telobox protein with telomere structure without appropriate evidence of its telomeric localisation and function.     

A stability switch for proteins

A paper published in the September 8 issue of Cell describes a generally applicable approach for chemical control of protein stability, with potential for broad use in chemical genetics.     

Astatine-211 labelled proteins and their stability in vivo

In an ongoing effort to obtain quantitative, rapid kit type labelling of [¹²³I] radiopharmaceuticals, we have examined organomercury precursors of [¹²³I] 15-(para-iodophenyl)-pentadecanoic acid (IPPA). Chloromercuri derivatives of phenyl pentadecanoic acid (PPA) and the PPA ethyl ester were obtained by mercuration utilizing mercuric trifluoroacetate in trifluoroacetic acid followed by treatment with acetic acid and hydrochloric acid. The most simple compound, chloromercuri PPA, proved insoluble at room temperature in the common solvents useful for radioiodination and purification. The study was extended in a systematic way to chloromercuri PPA ethyl ester and the acetoxy mercuri PPA ethyl ester. As expected, these two compounds posessed successively more useful ranges of solvent compatibility. Iodination and [¹²³I] radioiodination were carried out with the three compounds of PPA. Chloromercuri PPA was dissolved with difficulty in acetic acid at 70°C and 71% radiochemical yield of [¹²³I] IPPA was obtained during the course of a 5 minute reaction utilizing chloramine T. The chloromercuri PPA ethyl ester was dissolved in ethyl acetate/acetic acid (2/1 v/v) at room temperature and 87% radiochemical yield of [¹²³I] IPPA was obtained following 10 minutes reaction. With the acetoxy mercuri PPA ethyl ester it was possible to conduct the radioiodination in ethanol again using chloramine T. A modest radiochemical yield (r. y.) (51%) of [¹²³I] IPPA ethyl ester was obtained after 60 min. It was possible to enhance the radiochemical yield in the presence of lithium acetate (84% r. y.). The isomeric purity of the [¹²³I] IPPA ethyl ester was unexpectedly high (99.9% para) when the radioiodination was conducted at room temperature.     

Recombination of hydrogen and oxygen in the technical gaseous waste of nuclear power plants (I)

The recombination of hydrogen and oxygen in technical gaseous waste of nuclear power plants has been studied. A highly efficient catalyst for reacting H₂ with O₂ to form water was prepared. Various operating conditions and factors affecting the recombination of H₂ and O₂ were tested and the best conditions were determined. Results show that the Pd–Al₂O₃ catalyst prepared had very good characteristics. The recombination rate of H₂ and O₂ was higher than 98.3% and 99.9%, respectively. After recombination, residual concentrations of H₂ and O₂ in waste gas were O₂<3 ppm, H₂<400 ppm. The Pd–Al₂O₃ catalyst and operating conditions determined for gaseous waste processing of nuclear power plants were satisfactory.     

Binding of malachite green promotes stability and shows preference for a human telomere DNA G-quadruplex

A single-stranded human telomere DNA sequence can fold into an intramolecular G-quadruplex structure, which has been shown to inhibit telomerase activity. Small molecules that selectively target and stabilise the G-quadruplex structure have been proposed as potential anticancer drugs. In this study, we analysed the properties of binding of malachite green, a cationic triphenylmethane dye, to the G-quadruplex of d[(T₂AG₃)₄] by UV spectroscopy of thermal melting analysis, a competitive equilibrium dialysis assay, and absorption and circular dichroism spectroscopies. When binding to malachite green, the quadruplex structure that formed in the presence of K⁺ ions was stabilised with an increase in melting temperatures by 6 °C. Malachite green showed selective binding to the G-quadruplex in the presence of duplex and single-stranded DNAs, owing to which it presents higher potential for anticancer therapy, compared to other triphenylmethane dyes. The induced signals of circular dichroism indicate that the binding mode of malachite green involves intercalation between adjacent guanine tetrads of the G-quadruplex.     

Solution stability and variability in a simple model of globular proteins

It is well known among molecular biologists that proteins with a common ancestor and that perform the same function in similar organisms, can have rather different amino-acid sequences. Mutations have altered the amino-acid sequences without affecting the function. A simple model of a protein in which the interactions are encoded by sequences of bits is introduced, and used to study how mutations can change these bits, and hence the interactions, while maintaining the stability of the protein solution. This stability is a simple minimal requirement on our model proteins which mimics part of the requirement on a real protein to be functional. The properties of our model protein, such as its second virial coefficient, are found to vary significantly from one model protein to another. It is suggested that this may also be the case for real proteins in vivo.     

Phytochrome-dependent photomovement responses mediated by phototropin family proteins in cryptogam plants

In this review, we describe the regulation of photomovement responses by phototropin and phytochrome photoreceptors. The blue light receptor phototropin mediates various photomovement responses such as phototropism, chloroplast movement and stomatal opening. In cryptogamic plants including ferns, mosses and green alga, red as well as blue light mediates phototropism and chloroplast movement. The red/far-red light reversibility suggests the involvement of phytochrome in these responses. Thereby, plant growth is presumably promoted by coordinating these photomovements to capture efficiently light for photosynthesis.     

Chemistry in human telomere biology: structure, function and targeting of telomere DNA/RNA

Telomeres are present at the ends of all eukaryotic chromosomes. Human telomeres play an important role in critical processes underlying genome stability, cancer, and aging, and their importance was recognized via the award of the 2009 Nobel Prize in Physiology or Medicine. Chemistry has made vast and almost unparalleled contributions to telomere biology. This critical review highlights the contributions of chemistry in human telomeres and summarizes the significant development of human telomere biology. First, I provide an overview of the advances in understanding of the structures and functions of human telomeres. Second, I focus on the current efforts on developing various chemical approaches to targeting human telomeres and telomerase for the treatment of cancer. Third, studies on a newly discovered telomeric repeat-containing RNA are discussed in detail. Last, future challenges in the field are outlined, including perspectives of both chemistry and biology (412 references).     

Morphogenetic and chemical stability of long-term maintained Agrobacterium-mediated transgenic Catharanthus roseus plants

Transgenic Catharanthus roseus plants (transgenic Dhawal [DT] and transgenic Nirmal [NT]) obtained from the Agrobacterium tumefaciens and Agrobacteriumrhizognenes-mediated transformations, respectively, have been maintained in vitro for 5 years. Plants were studied at regular intervals for various parameters such as plant height, leaf size, multiplication rate, alkaloid profile and presence of marker genes. DT plant gradually lost the GUS gene expression and it was not detected in the fifth year while NT plant demonstrated the presence of genes rolA, rolB and rolC even in the fifth year, indicating the more stable nature of Ri transgene. Vindoline content in the DT was two times more than in non-transformed control plants. Alkaloid and tryptophan profiles were almost constant during the 5 years. The cluster analysis revealed that the DT plant is more close to the control Nirmal plant followed by NT plant.     

LEA proteins in higher plants: structure, function, gene expression and regulation

Late embryogenesis abundant (LEA) proteins are mainly low molecular weight (10–30 kDa) proteins, which are involved in protecting higher plants from damage caused by environmental stresses, especially drought (dehydration). These findings and the fact that the breeding of drought tolerant varieties would be of great value in agriculture, form the basis of search for anti-drought inducible genes and their characterization. LEA proteins are generally classified into six groups (families) according to their amino acid sequence and corresponding mRNA homology, which are basically localized in cytoplasm and nuclear region. LEA protein synthesis, expression and biological activities are regulated by many factors (e.g. developmental stages, hormones, ion change and dehydration), signal transduction pathways and lea genes. No tissue-specific lea gene expression has been considered as one main regulatory mechanism on the basis of extensive studies with the model plant, Arabidopsis thaliana. The study of the regulatory mechanism of lea gene expression is an important feature of modern plant molecular biology.     

Thermal stability limits of proteins in solution and adsorbed on a hydrophobic surface

A coarse-grained Monte Carlo simulation is used to study thermal denaturation of small proteins in an infinitely dilute solution and adsorbed on a flat hydrophobic surface. Intermolecular interactions are modeled using the Miyazawa-Jernigan (MJ) knowledge-based potential for implicit solvent with the BULDG hydrophobicity scale. We analyze the thermal behavior of lysozyme for its prevalence of α-helices, fibronectin for its prevalence of β-sheets, and a short single helical peptide. Protein dimensions and contact maps are studied in detail before and during isothermal adsorption and heating. The MJ potential is shown to correctly predict the native conformation in solution under standard conditions, and the anticipated thermal stabilization of adsorbed proteins is observed when compared with heating in solution. The helix of the peptide is found to be much less stable thermally than the helices of lysozyme, reinforcing the importance of long-range forces in defining the protein structure. Contact map analysis of the adsorbed proteins shows correlation between the hydrophobicity of the secondary structure and their thermal stability on the surface.     

Cationic peptides and proteins from seeds of plants of the family Malvaceae

Total cationic peptides from seeds of plants of the family Malvaceae were separated by chromatography. The molecular weights of the isolated peptides were determined by MALDI-TOF mass spectroscopy. The antifungal activity of total cationic peptides from seeds of plants of this family against Phytophtora infestans was demonstrated on potato disks.     

The effect ofpH on thermal stability of globular proteins

In this study we try to re-analyze thepH dependence of thermal stability of small globular proteins. From the thermodynamic point of view a long series of calorimetric and spectroscopic investigations has shown that the decreased stability in very acidic conditions can be ascribed to entropic effects. The same conclusion is reached, from a microscopic point of view, by assuming that a binding of protons on equal and noninteracting sites takes place as a consequence of unfolding process. By linking the conformational unfolding equilibrium to the proton binding equilibrium, a model is developed that is able to describe the dependence on thepH of the thermal denaturation processes of small globular protiens. The application of the model to hen lysozyme and T4 lysozyme correctly accounts for the experimental results.     

Recombination emission in hydrogen-fluorine systems

Visible emission which is generated when H₂ is added to partially dissociated F₂ is found to be due to Δυ = 4, 5, and 6 transitions of HF(X). The temporal and stoichiometric dependence of this emission strongly suggests that it results from direct combination of hydrogen and fluorine atoms and/or from recombination of hydrogen atoms with subsequent transfer of vibrational energy from H₂ to HF.