DNA-Polylactide Modified Biosensor for Electrochemical Determination of the DNA-Drugs and Aptamer-Aflatoxin M1 Interactions

DNA sensors were assembled by consecutive deposition of thiacalix[4]arenes bearing oligolactic fragments, poly(ethylene imine), and DNA onto the glassy carbon electrode. The assembling of the layers was monitored with scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The configuration of the thiacalix[4]arene core determined self-assembling of the polymeric species to the nano/micro particles with a size of 70–350 nm. Depending on the granulation, the coatings show the accumulation of a variety of DNA quantities, charges, and internal pore volumes. These parameters were used to optimize the DNA sensors based on these coatings. Thus, doxorubicin was determined to have limits of detection of 0.01 nM (cone configuration), 0.05 nM (partial cone configuration), and 0.10 nM (1,3-alternate configuration of the macrocycle core). Substitution of native DNA with aptamer specific to aflatoxin M1 resulted in the detection of the toxin in the range of 20 to 200 ng/L (limit of detection 5 ng/L). The aptasensor was tested in spiked milk samples and showed a recovery of 80 and 85% for 20 and 50 ng/L of the aflatoxin M1, respectively.

The Topological City

The Topological City is a design concept for a three-dimensional city in China. To accommodate future populations, cities need to be dense, diverse and ecological. Minimising the physical dimension reduces the consumption of material and energy and the destruction of ecological and agricultural landscapes. Mixed-use cities reduce the time, energy and congestion of travel. The integration of natural systems improves environmental quality and supports biodiversity. Ultimately however, the quality and functionality of contemporary urban life relies on dynamics of economic, social and intellectual interaction. The design form of a city must facilitate exchange between heterogeneous and changing programs while minimising energy and maximising habitat. High-rise construction is the dominant morphology of modern cities. Generated by an extrusion from the ground toward the sky, high-rise adds significant density but results in circulatory dead ends, structural inefficiency and habitat disconnectedness. High-rise is not interactive, energy efficient, or ecological. The Topological City proposes an alternate configuration of the urban environment. Drawing on the theory of place and connection known as ‘topology’, it constructs a three-dimensional network of vertical and horizontal towers, connected and activated by circulation. The Topological City is dense, diverse, ecological and interactive, suggesting a potential new direction for sustainable urban form.

A Kv channel with an altered activation gate sequence displays both “fast” and “slow” activation kinetics

The Kv1–4 families of K+ channels contain a tandem proline motif (P XP) in the S6 helix that is crucial for channel gating. In human Kv1.5, replacing the first proline by an alanine resulted in a nonfunctional channel. This mutant was rescued by introducing another proline at a nearby position, changing the sequence into AVPP. This resulted in a channel that activated quickly (ms range) upon the first depolarization. However, thereafter, the channel became trapped in another gating mode that was characterized by slow activation kinetics (s range) with a shallow voltage dependence. The switch in gating mode was observed even with very short depolarization steps, but recovery to the initial “fast” mode was extremely slow. Computational modeling suggested that switching occurred during channel deactivation. To test the effect of the altered P XP sequence on the mobility of the S6 helix, we used molecular dynamics simulations of the isolated S6 domain of wild type (WT) and mutants starting from either a closed or open conformation. The WT S6 helix displayed movements around the P XP region with simulations starting from either state. However, the S6 with a AVPP sequence displayed flexibility only when started from the closed conformation and was rigid when started from the open state. These results indicate that the region around the P XP motif may serve as a “hinge” and that changing the sequence to AVPP results in channels that deactivate to a state with an alternate configuration that renders them “reluctant” to open subsequently.

Orientation of diplochromosomes in mitoses of potato (Solatium tuberosum L.) callus cultures

The mitotic behaviour of diplochromosomes was investigated in early calli from leaf segments of a monohaploid potato (x = 12) with the aid of the fluorescent plus Giemsa technique. The sister chromosomes of the diplochromosomes do not separate during metaphase because the inner chromatids remain connected. Consequently the diplochromosomes orient in three stable configurations during metaphase. In the case in which sister chromosomes become auto-oriented, the outer chromatids face one pole and the inner chromatids the opposite pole (U-shaped configuration), or the outer and inner chromatid of each sister chromosome face different poles (alternate configuration). Less frequently the sister chromosomes become oriented to different poles (C-shaped configuration). Linear orientation is not observed. At least until the onset of telophase only the inner chromatids originating from U-shaped configurations may remain paired, but they fall apart before the next metaphase. The mitoses with diplochromosomes give rise to two cells with double the number of chromosomes.Key words: potato, diplochromosomes, mitosis, orientation, polyploidization.

The Attitude Control System as an Integral Part of the V/STOL Propulsion System Installation

The analytical techniques for evaluating the design and weight penalties associated with the V/STOL attitude control system are presented. A comparison is made between a V/STOL 200-passenger transport which uses thrust modulation of the lift engines for attitude control in the roll mode versus an alternate configuration which uses roll control fans driven by individual gas generators. The configuration using lift engine thrust modulation for roll control shows a 4729-lb weight advantage.