oa Editorial {Hot topic: QSPR Models for Computer-Aided Drug Design in Microbiology, Parasitology, and Pharmacology (Guest Editor: Humberto Gonzalez-Diaz)]

In our days, there has been an explosion on the use of Quantitative Structure-Property Relationships (QSPR) models for any kind of bio-systems in principle. We see QSPR model as a function that predict the properties of the system (drug, protein, RNA, proteome, diseasome) using parameters that numerically describe the structure of the system. In particular Topological Indices (TIs) are numerical parameters that quantify the structure of Graphs and Complex Networks used to represent the molecular, social, technological, and/or bio-systems. Using TIs as inputs we can find different types of QSPR-like models that fit to more specific situations, for instance Quantitative Structure-Activity Relationships (QSAR), Quantitative Structure- Toxicity Relationships (QSTR) or Quantitative Structure-Reactivity Relationships (QSRR), to cite a few examples. In all these cases, we can find models that use the TIs of the system as input to predict the properties of this system (output), see the recent book edited by Gonzalez-Diaz and Munteanu in 2010 [1]. In a recent, preliminary review in the field published in Proteomics in 2008 Gonzalez-Diaz et al. discussed the use of these methods but only from the point of view of proteins [2]. Next we extended the discussion to a number of authors editing special issues on Current Topics in Medicinal Chemistry in 2008 [3-12], Current Proteomics in December 2009 [13-19], Current Drug Metabolism [20-28] and Current Pharmaceutical Design in 2010 [29-37], and Current Bioinformatics in 2011 [38-47]. Taking all the previous aspects into consideration we decided to guest-edit the present hot-topic issue for Current Computer- Aided Drug Design. The main aim of the issue is to review and discuss new trends in the use of QSAR/QSPR-like methods, networks theory, and TIs in CADD. In the first paper, Jayadeepa et al. [48] (from Bangalore, INDIA) focused their attention on CADD study of the drug target 5-α-reductase (5αR), which is important in prostate cancer. In the second paper, Speck-Planche and Cordeiro [49] (REQUIMTE/Department of Chemistry and Biochemistry, University of Porto, Portugal) focus on CADD approach for the design of novel anti-HIV drugs. In the third paper, Garcia, Fall, and Gomez [50] (from University of Vigo, Spain) deal with DNA polymerases, essential enzymes for DNA replication, repair and recombination. In the next work, Dave et al. [51] (from Sardar Patel University, Gujarat; India) discuss CADD techniques for exploration of drug target in H1N1 strain is hemagglutinin. The following paper [52] gives a review of Synthesis, Biological assay, and QSAR studies of β- secretase inhibitors, important for Alzheimer's disease (AD). After that, a group of authors coordinated by Khan (from Genok - Center for Biosafety, Tromso, Norway and Ankara University, Turkey) presented a work [53] where they studied two alkaloids namely (+)-buxabenzamidienine and (+)-buxamidine from Buxus sempervirens, using bioassay-guided fractionation and isolation method. Next, Concu (from University of Cagliari, Italy) and Shen (from Center for Systems Biology, Soochow University, China) et al. [54] reviewed CADD studies on Collagen, the most abundant protein of the whole human body, and its instability being related to a number of important diseases like osteogenesis imperfect, Ehlers-Danlos Syndrome, Collagenopathy. In the following paper, Chis et al. [55] (a team of authors from Institute for Marine Research (IIM-CSIC), Vigo, Spain, and West University of Timisoara, Romania) considered models of interaction between the immune system and tumor cells. Next, another paper [56] by authors from the University of Santiago, Cuba, and University of Porto, Portugal focused CADD techniques applied to pesticides design. In the last work [57], we intend to offer a common background and withdrawn general conclusions to all the manuscripts presented in this special issue making emphasis on the generalization of QSAR/QSPR and Complex network tools inside/outside CADD. In so doing, we have made a review of more common types of complex networks involving drugs or their targets. We expect that the present issue may become an interesting resource for all those authors interested in classic methods and new trends in CADD. With this aim, the issue groups 10 papers with the opinion of more than 50 researchers. These authors come from known institutions of Asia (China, India, Turkey), America (US, Cuba), and the EU (Spain, Portugal, Romania, Italy, and Norway). I would like to express here my gratitude to all these authors for their kind contribution. I also acknowledge the kind attention and collaboration of both teams, the editorial board of the journal Current Computer-Aided Drug Design (CCADD) and Bentham Science Publishers; with special mention to Editor Prof. Subhash C. Basak and Publication Manager Ms. Madiha Rauf, respectively.....