The Italian journal of biochemistry最新文献

Bovine serum albumin (BSA) has various applications in blood group serology and different research purposes. In this study purification of BSA has been compared with human serum albumin (HSA) using modified ethanol precipitation method based on the method of Cohn. The purification process was carried out under controlled conditions, particularly of ethanol concentration, pH, ionic strength and temperature. It was revealed that the produced BSA and HSA have purity more than 95%. It is obvious that HSA can be used, as a drug when the amount of its polymers is less than 5% whereas polymer generation is required in order to enhance the potentiating properties of BSA in agglutination of red cells. We propose here a simple and rapid two-step method for simultaneously purification and polymerization of BSA. By this method simply BSA with desired amount of polymers was obtained by 40% ethanol concentration.

Two Myrtus communis varieties (var. italica and baetica) were studied in order to investigate their essential oil yield and composition. Essential oil yield varied in leaves, fruits and stems. So, in leaves, it was 0.5% for italica and 0.3% for baetica and was higher than in fruits and stems with respectively 0.1% and 0.04% for italica and 0.07% and 0.03% for baetica. The essential oil analysis performed by GC and GC/MS showed a composition characterized by a high percentage of monoterpene hydrocarbons in leaves, largely due to alpha-pinene with 51.3% for italica and 27.7% for baetica; 1,8-cineole, the alone compound of ether class, was predominant in fruits and stems with respectively 31.6% and 34.7% for italica and 19.8% and 25.8% for baetica.

Estimation of total and direct bilirubin in serum plays an important role in differential diagnosis of hyperbilirubinemia. Several direct spectrophotometric methods are commercially available for total and direct bilirubin estimation in which the amount of the sample (serum) varies from 200 ml to 800 ml. It is difficult to collect such amount of serum from infants, as neonatal jaundice is the most common problem in this age group. To overcome this problem modified micro assay method was developed using dimethylsulfoxide (DMSO). The amount of the serum sample is reduced from 100 ml to 20 ml per test for both total and direct bilirubin. A method comparison study was performed using 100 consecutive serum samples, by modified micro assay method and a reference Jendrassik-Grof method. Total bilirubin in these human serum samples ranged from 0.4-15.0 mg/dl and direct bilirubin ranged from 0.05-12.0 mg/dl. The results conclude that modified micro assay method had significant correlation with r-value of 0.99989 for total serum bilirubin and with r-value of 0.99971 for direct serum bilirubin. Linearity of the method is 20 mg/dl and 15 mg/dl for total and direct bilirubin, respectively. Monoreagent used during the assay is stable for 24 hours at 2-8 degrees C while the kit is stable for one year at 2-8 degrees C. In conclusion this micro assay method is rapid, reliable, simple and accurate for the estimation of total and direct bilirubin with small serum quantities. It is equally reliable for manual; semi automated and automated chemistry analyzers.

Reverse gyrase is the only DNA topoisomerase capable of introducing positive supercoiling into DNA molecules. This unique activity reflects a distinctive arrangement of the protein, which is composed of a topoisomerase IA module fused to a domain containing sequence motives typical of helicases; however, reverse gyrase works neither like a canonical topoisomerase IA nor like a helicase. Extensive genomic analysis has shown that reverse gyrase is present in all organisms living above 70 degrees C and in some of those living at 60- 70 degrees C, but is invariably absent in organisms living at mesophilic temperatures. For its peculiar distribution and biochemical activity, the enzyme has been suggested to play a role in maintenance of genome stability at high temperature. We review here recent phylogenetic, biochemical and structural data on reverse gyrase and discuss the possible role of this enzyme in the biology of hyperthermophilic organisms.

In recent years growing evidence has suggested that the RecQ helicases play a crucial role in preserving genome stability. The importance of this observation in humans is substantiated by the fact that the absence of a functional RecQ helicase is associated with genetic syndromes characterised by elevated predisposition to a wide variety of cancers. It is well recognized that maintenance of genome integrity relies on the accurate execution of the DNA replication process as well as on efficient DNA repair. A number of studies have described interactions of RecQ helicases with topoisomerases and it has been proposed that this cooperation may be essential for cell viability and the avoidance of cancer development in human cells.

Borago officinalis rosette leaves were sampled in the region of Amdoun (Tunisia) during different stages of their development. Essential oil contents varied from 0.01% to 0.13% respectively in young and adult leaves. Twenty three volatile compounds were identified. Hydrocarbons, mainly represented by nonadecane (29.8%), tetracosane (11.3%) and heptacosane (4.7%), constituted the major class in the young leaves (45.8%), followed by aldehydes (22.4%). The percentages of these two classes decreased to reach respectively 15% and 8.1% in adult leaves in favour of alcohols (57.9%) where cis-3-hexenol (29.6%) and hexanol (14.5%) were the main compounds. Total fatty acids amounts increased from 5.03 mg/g DW in young leaves to 32.23 mg/g DW in adult ones. The predominant fatty acids were alpha-linolenic (C18:3 n-3), stearidonic (C18:4 n-3), gamma-linolenic (C18:3 n-6), palmitic (C16: 0) and linoleic (C18:2 n-6) acids.

Cells are continuously under the assault of endogenous and exogenous genotoxic stress that challenges the integrity of DNA. To cope with such a formidable task cells have evolved surveillance mechanisms, known as checkpoints, and a variety of DNA repair systems responding to different types of DNA lesions. These lesions occur in the context of the chromatin structure and, as expected for all DNA transactions, the cellular response to DNA damage is going to be influenced by the chromatin enviroment. In this review, we will discuss recent studies implicating chromatin remodelling factors and histone modifications in the response to DNA double-strand breaks (DSBs) and in checkpoint activation in response to UV lesions.

Immobilization of dextransucrase from Leuconostoc mesenteroides PCSIR-4 on alginate is optimized for application in the production of dextran from sucrose. Dextransucrase was partially purified by ethanol upto 2.5 fold. Properties of dextransucrase were less affected by immobilization on alginate beads from soluble enzyme. Highest activities of both soluble and immobilized dextransucrase found to be at 35 degrees C and optimum pH for activity remain 5.00. Substrate maxima for immobilized enzyme changed from 125 mg/ml to 200 mg/ml. Incubation time for enzyme-substrate reaction for maximum enzyme activity was increased from 15 minutes to 60 minutes in case of immobilized enzyme. Maximum stability of immobilized dextransucrase was achieved at 25 degrees C with respect to time.

Spirulina platensis (=Arthrospira platensis) is a tunisian strain which has been isolated for the first time in Oued Essed (Sousse, Sidi Bou Ali). Biomass evolution, proteins, chlorophylls and fatty acids composition of this alga were monitored by varying nitrogen concentrations in the culture medium. Nitrogen stress was provoked by adding sodium nitrate (NaNO3) in the culture medium with concentrations varying from 0 to 5 g/l. Results obtained showed that nitrogen depletion increased total proteins and total chlorophylls. The addition of NaNO3 (5g/l) led to an increase of total fatty acids amounts and modify fatty acids composition. Optimal quantities of palmitic, gamma -linolenic and oleic acids were obtained with NaNO3 free-cultures. Thus, the tunisian strain has valuable biological substances, worthy to determine the optimal conditions for its propagation.

Human DNA Topoisomerase I is a 765aa monomeric enzyme composed of four domains: the N-terminal domain, highly charged and responsible for several protein-protein interactions, the core domain that embraces the DNA during catalysis, the highly charged linker domain and the C-teminal domain containing the active site. The enzyme promotes the relaxation of supercoiled DNA by nicking and rejoining one of the strands of the DNA. Its activity is critical for many biological processes including DNA replication, transcription, and recombination. The aim of this review is to analyze the enzyme activity in terms of structure-function relationship.