DNA-Interactive Properties of Crotamine, a Cell-Penetrating Polypeptide and a Potential Drug Carrier

Crotamine, a 42-residue polypeptide derived from the venom of the South American rattlesnake Crotalus durissus terrificus, has been shown to be a cell-penetrating protein that targets chromosomes, carries plasmid DNA into cells, and shows specificity for actively proliferating cells. Given this potential role as a nucleic acid-delivery vector, we have studied in detail the binding of crotamine to single- and double-stranded DNAs of different lengths and base compositions over a range of ionic conditions. Agarose gel electrophoresis and ultraviolet spectrophotometry analysis indicate that complexes of crotamine with long-chain DNAs readily aggregate and precipitate at low ionic strength. This aggregation, which may be important for cellular uptake of DNA, becomes less likely with shorter chain length. 25-mer oligonucleotides do not show any evidence of such aggregation, permitting the determination of affinities and size via fluorescence quenching experiments. The polypeptide binds non-cooperatively to DNA, covering about 5 nucleotide residues when it binds to single (ss) or (ds) double stranded molecules. The affinities of the protein for ss-vs. ds-DNA are comparable, and inversely proportional to salt levels. Analysis of the dependence of affinity on [NaCl] indicates that there are a maximum of,3 ionic interactions between the protein and DNA, with some of the binding affinity attributable to non-ionic interactions. Inspection of the three-dimensional structure of the protein suggests that residues 31 to 35, Arg-Trp-Arg-Trp-Lys, could serve as a potential DNA-binding site. A hexapeptide containing this sequence displayed a lower DNA binding affinity and salt dependence as compared to the full-length protein, likely indicative of a more suitable 3D structure and the presence of accessory binding sites in the native crotamine. Taken together, the data presented here describing crotamine-DNA interactions may lend support to the design of more effective nucleic acid drug delivery vehicles which take advantage of crotamine as a carrier with specificity for actively proliferating cells. Citation: Chen P-C, Hayashi MAF, Oliveira EB, Karpel RL (2012) DNA-Interactive Properties of Crotamine, a Cell-Penetrating Polypeptide and a Potential Drug Carrier. PLoS ONE 7(11): e48913. doi:10.1371/journal.pone.0048913

Quality of life among Brazilian women living with HIV/AIDS

The purpose of the present study was to assess quality of life (QoL) in Brazilian women living with HIV/AIDS, according to the World Health Organization Quality of Life HIV-BREF (WHOQoL-HIV-BREF) domains. A quantitative-based, cross-sectional, analytical study was carried out in healthcare centers specialized in assisting people living with HIV/AIDS, located in a municipality of the state of Sao Paulo, Brazil. One hundred and six women of age 18 years or more, users of the public healthcare system, participated in the study. Socio-demographic and clinical variables were collected using a specific questionnaire. Quality of life related variables were collected by means of the WHOQoL-HIV-BREF instrument. As per the QoL domains, study results show that the Spirituality domain reached a standardized mean score of 65.7, followed by the Physical (64.7), Psychological (60.6), Social Relationships (59.5), Independence (58.6), and Environment (54.5) domains. Results of the multiple regression analysis indicate that the women's employment or retirement, income greater than the minimum wage, and higher educational level were associated with a higher standardized mean score of QoL. However, recent HIV/AIDS diagnosis and exposure to antiretroviral agents for a period shorter than two years were negatively associated with QoL. It is critical that public policies favor an all-embracing social inclusion of these women, thus promoting better social conditions. Counseling, clinical follow-up immediately after the infection diagnosis, and initiation of antiretroviral treatment are crucial moments in the lives of these individuals.