The electronic spin filtering capability of a single chiral helical peptide is measured. A ferromagnetic electrode source is employed to inject spin-polarized electrons in an asymmetric single-molecule junction bridging an α-helical peptide sequence of known chirality. The conductance comparison between both isomers allows the direct determination of the polarization power of an individual chiral molecule.

Efficient intracellular drug delivery and target specificity are often hampered by the presence of biological barriers. Thus, compounds that efficiently cross cell membranes are the key to improving the therapeutic value and on-target specificity of non-permeable drugs. The discovery of cell-penetrating peptides (CPPs) and the early design approaches through mimicking the natural penetration domains used by viruses have led to greater efficiency of intracellular delivery. Following these nature-inspired examples, a number of rationally designed CPPs has been developed. In this review, a variety of CPP designs will be described, including linear and flexible, positively charged and often amphipathic CPPs, and more rigid versions comprising cyclic, stapled, or dimeric and/or multivalent, self-assembled peptides or peptido-mimetics. The application of distinct design strategies to known physico-chemical properties of CPPs offers the opportunity to improve their penetration efficiency and/or internalization kinetics. This led to increased design complexity of new CPPs that does not always result in greater CPP activity. Therefore, the transition of CPPs to a clinical setting remains a challenge also due to the concomitant involvement of various internalization routes and heterogeneity of cells used in the in vitro studies.

The mutations in the quinolone resistance-determining region of the gyrA and gyrB genes from 27 clinical isolates of Escherichia coli with a range of MICs of ciprofloxacin from 0.007 to 128 ,ug/ml and of nalidixic acid from 2 to >2,000 ,ug/ml were determined by DNA sequencing. All 15 isolates with ciprofloxacin MICs of .1 ,ug/ml showed a change in Ser-83 to Leu of GyrA protein, whereas in clinical isolates with a MIC of .8 ,ug/ml (11 strains), a double change in Ser-83 and Asp-87 was found. All isolates with a MIC of nalidixic acid of .128 ,ug/ml showed a mutation at amino acid codon Ser-83. Only 1 of the 27 clinical isolates of E. coli analyzed showed a change in Lys-447 of the B subunit of DNA gyrase. A change in Ser-83 is sufficient to generate a high level of resistance to nalidixic acid, whereas a second mutation at Asp-87 in the A subunit of DNA gyrase may play a complementary role in developing the strain's high levels of ciprofloxacin resistance.New fluoroquinolones are broad-spectrum antibacterial agents which inhibit DNA gyrase activity (26). DNA gyrase contains two subunits of GyrA and two subunits of GyrB (13,19). Gyrase A mediates DNA strand breakage and reunion with the Tyr residue at position 122 forming a transient phosphotyrosine linkage with a broken DNA strand. The mechanisms of quinolone resistance essentially fall into two classes: (i) mutations in gyrA (1,2,5,6,8,17,28,30) or gyrB genes (27, 29) or (ii) reduced levels of quinolone accumulation in the cells (3, 4, 9-12). The mutations in the gyrA gene involved in the resistance are clustered in a region between nucleotides 199 (Ala-67) and 318 (Gln-106), which contains nucleotide 247 (Ser-83), the most frequently changed in spontaneus gyrA mutations. In the gyrB gene, two quinolone resistance-determining sites (amino acids 426 and 447) have been found (27,29). The mutation at amino acid codon Asp-426 confers resistance to nalidixic acid and the new fluoroquinolones, whereas the change of Lys-447 results in resistance to nalidixic acid and increased susceptibility to the fluoroquinolones (29). Recently, Heisig et al. (8) identified mutations in the gyrA gene of Escherichia coli 205096, a highly fluoroquinolone-resistant strain (MIC of ciprofloxacin, 128 ,ug/ml). From 1989 to 1993, the level of resistance to ciprofloxacin in our hospital increased from 0 to 16% in E. coli isolated from urine samples. To further assess the importance of these gyrA and gyrB mutations in the acquisition of high-level quinolone resistance, we examined by DNA sequencing 27 clinical isolates of E. coli with a range of MICs of ciprofloxacin from 0.007 to 128 ,ug/ml and of nalidixic acid from 2 to >2,000 ,ug/ml.The clinical isolates of E. coli were obtained from urine samples from outpatients, who had not previously received quinolones,

Parkinson’s disease (PD) is characterized by a progressive loss of dopaminergic neurons, a process that current therapeutic approaches cannot prevent. In PD, the typical pathological hallmark is the accumulation of intracellular protein inclusions, known as Lewy bodies and Lewy neurites, which are mainly composed of α-synuclein. Here, we exploited a high-throughput screening methodology to identify a small molecule (SynuClean-D) able to inhibit α-synuclein aggregation. SynuClean-D significantly reduces the in vitro aggregation of wild-type α-synuclein and the familiar A30P and H50Q variants in a substoichiometric molar ratio. This compound prevents fibril propagation in protein-misfolding cyclic amplification assays and decreases the number of α-synuclein inclusions in human neuroglioma cells. Computational analysis suggests that SynuClean-D can bind to cavities in mature α-synuclein fibrils and, indeed, it displays a strong fibril disaggregation activity. The treatment with SynuClean-D of two PD Caenorhabditis elegans models, expressing α-synuclein either in muscle or in dopaminergic neurons, significantly reduces the toxicity exerted by α-synuclein. SynuClean-D–treated worms show decreased α-synuclein aggregation in muscle and a concomitant motility recovery. More importantly, this compound is able to rescue dopaminergic neurons from α-synuclein–induced degeneration. Overall, SynuClean-D appears to be a promising molecule for therapeutic intervention in Parkinson’s disease.