An in silico computational technique for predicting peptide sequences that can be cyclized by cyanobactin macrocyclases, e.g., PatGmac, is reported. We demonstrate that the propensity for PatGmac-mediated cyclization correlates strongly with the free energy of the so-called pre-cyclization conformation (PCC), which is a fold where the cyclizing sequence C and N termini are in close proximity. This conclusion is driven by comparison of the predictions of boxed molecular dynamics (BXD) with experimental data, which have achieved an accuracy of 84%. A true blind test rather than training of the model is reported here as the in silico tool was developed before any experimental data was given, and no parameters of computations were adjusted to fit the data. The success of the blind test provides fundamental understanding of the molecular mechanism of cyclization by cyanobactin macrocyclases, suggesting that formation of PCC is the rate-determining step. PCC formation might also play a part in other processes of cyclic peptides production and on the practical side the suggested tool might become useful for finding cyclizable peptide sequences in general.

Macrocyclic peptides have promising therapeutic potential but the scaling up of their chemical synthesis is challenging. The cyanobactin macrocyclase PatGmac is an efficient tool for production but is limited to substrates containing 6-11 amino acids and at least one thiazoline or proline. Here we report a new cyanobactin macrocyclase that can cyclize longer peptide substrates and those not containing proline/thiazoline and thus allows exploring a wider chemical diversity.

Peptide macrocycles are found in many biologically active natural products. Their versatility, resistance to proteolysis and ability to traverse membranes has made them desirable molecules. Although technologies exist to synthesize such compounds, the full extent of diversity found among natural macrocycles has yet to be achieved synthetically. Cyanobactins are ribosomal peptide macrocycles encompassing an extraordinarily diverse range of ring sizes, amino acids and chemical modifications. We report the structure, biochemical characterization and initial engineering of the PatG macrocyclase domain of Prochloron sp. from the patellamide pathway that catalyzes the macrocyclization of linear peptides. The enzyme contains insertions in the subtilisin fold to allow it to recognize a three-residue signature, bind substrate in a preorganized and unusual conformation, shield an acylenzyme intermediate from water and catalyze peptide bond formation. The ability to macrocyclize a broad range of nonactivated substrates has wide biotechnology applications.

X-irradiated Palm Oil of the Elaeis guineensis specie was studied by assessing the effect of the radiation on the Peroxide, Iodine and Fatty acid values of the oil. These were compared with values of fresh and thermoxidized palm oil. Results showed a rise in the peroxide value by as much as 52.5% for thermoxidized oil and 25.2% for xirradiated oil; and iodine values similarly increasing by 6.4% for thermoxidized oil and 3.5% for x-irradiated palm oil respectively, while the Acid value increased by as much as 460% and 683% for thermoxidized and xirradiated samples respectively. These are strong indications of the deterioration of the oil, the attendant consequences of which are discussed. West African Journal of Radiology Vol.7(1) 2000: 30-34

In vitro Sodium Chloride absorption of X-rays was studied with concentrations of 46 mg/mol to 460 mg/mol, which include the range of sodium and chloride ion concentrations in the human body. Irradiation was done with an incident x-radiation dose equivalent of 0.0309 m Sv, with Lithium Fluoride as detector. Absorbed doses read off the thermoluminiscent detectors (TLD) with a TLD reader showed a non uniform variation, but linear relationship between concentration and absorbed dose, with a strong positive correlation of 0.8140. The radiobiological implications of these results are discussed. Keywords: Sodium Chloride, X-ray, Absorption, concentration, phosphors, selection, patients (Global Journal of Pure and Applied Sciences: 2002 9(1): 133-138)

The effect of bilirubin concentration on dose equivalent of absorbed radiation was investigated in vitro in this study. Different concentrations of bilirubin were exposed to a fixed dose equivalent x-ray irradiation from an R501 x-ray generator. The fraction of radiation transmitted and the fraction absorbed were measured using LiF (TLD 100) chips as detectors, and the radiation absorbed by bilirubin was computed. Results indicate that at low concentrations (25 mol/L to 76 mol/L) absorbed doses decreased with increase in bilirubin concentration. At higher bilirubin concentrations (76 mol/L to 460 mol/L) and beyond, there was an increase in absorption with a strong positive correlation (r = 0.92) between dose absorbed and bilirubin concentration. The possible applications of this property of bilirubin as a modifier at high concentrations--- to enhance radiation effect on diseased tissue during radiotherapy, and the danger inherent presenting neonates for radiodiagnostic examinations are discussed. Global Journal of Pure and Applied Sciences Volume , No 1 January (2001) pp. 143-146 KEY WORDS: Bilirubin, radiation, absorption, radiotherapy, modifier.