The entrapment of chiral guests with gated baskets: can a kinetic discrimination of enantiomers be governed through gating?

The capacity of gated hosts for controlling a kinetic discrimination between stereoisomers is yet to be understood. To conduct corresponding studies, however, one needs to develop chiral, but modular and gated hosts. Accordingly, we used computational (RI-BP86/TZVP//RI-BP86/SV(P)) and experimental (NMR/CD/UV/Vis spectroscopy) methods to examine the transfer of chirality in gated baskets. We found that placing stereocenters of the same kind at the rim (R(1) =CH3, so-called bottom) and/or top amide positions (R(2) =sec-butyl) would direct the helical arrangement of the gates into a P or M propeller-like orientation. With the assistance of (1)H NMR spectroscopy, we quantified the intrinsic (thermodynamic) and constrictive (kinetic) binding affinities of (R)- and (S)-1,2-dibromopropane 5 toward baskets (S3b/P)-2, (S3t/M)-3, and (S3bt/P)-4. Interestingly, each basket has a low ( ≤1.3 kcal mol(-1)), but comparable (de<10%) affinity for entrapping enantiomeric (R/S)-5. In terms of the kinetics, basket (S3b/P)-2, with a set of S stereocenters at the bottom and P arrangement of the gates, would capture (R)-5 at a faster rate (kin(R)/kin(S) =2.0±0.2). Basket (S3t/M)-3, with a set of S centers at the top and M arrangement of the gates, however, trapped (S)-5 at a faster rate (kin(R)/kin(S) =0.30±0.05). In light of these findings, basket (S3bt/P)-4, with a set of S stereocenters installed at both top and bottom sites along with a P disposition of the gates, was found to have a lower ability to differentiate between enantiomeric (R/S)-5 (kin(R)/kin(S) =0.8). Evidently, the two sets of stereocenters in this "hybrid" host acted concurrently, each with the opposite effect on the entrapment kinetics. Gated baskets are hereby established to be a prototype for quantifying the kinetic discrimination of enantiomers through gating and elucidating the electronic/steric effects on the process.

Native Non-Saccharomyces Yeasts as a Tool to Produce Distinctive and Diverse Tamjanika Grape Wines.

The enological potential of two previously characterized indigenous yeast isolates, Hanseniaspora uvarum S-2 and Candida famata WB-1, in pure and sequential inoculation with commercial yeast Saccharomyces cerevisiae QA23 were analyzed in industrial-scale vinification of the grape variety Tamjanika. Their contribution to the quality and aroma profile was investigated by quantifying volatile compounds and wine sensory evaluation. Both yeast isolates were able to complete alcoholic fermentation, to reduce ethanol concentration up to 1.06% v/v (in monoculture) in comparation to S. cerevisiae QA23, and to enhance aroma and sensory profile. Based on calculated odor activity values (OAV), p-cymene, ethyl hexanoate, ethyl octanoate, and ethyl decanoate were the major aroma volatile compounds in all Tamjanika wine samples. Analyzed yeast strains significantly affected relative contribution of volatile compounds and can be considered responsible for the differences and uniqueness of the obtained wine samples. Besides confirmation of good enological and fermentative characteristics, selected isolates can be characterized as high ester-producing strains with potential to enhance the floral and fruity aromas of wine. The present study represents a further step toward the use of indigenous yeast isolates at industrial-scale fermentation in order to ensure the regional signature of Tamjanika wine.

A stereodynamic and redox-switchable encapsulation-complex containing a copper ion held by a tris-quinolinyl basket.

We investigated the coordination of Cu(I)/Cu(II) ions to chiral basket (S(3))-1. The results of both experimental and computational studies suggest the formation of a copper redox-switchable system capable of entrapping CH(3)CN.

[Meningitis as cochlear implant complication].

Over the last several decades, cochlear implantation has been fully proven as the treatment for profound hearing losses. The direct electrical stimulation of the spiral ganglion hair cells through the electrode inserted in the cochlear scala tympani is the essence of the cochlear implant (CI) functioning. Modern technological development has introduced unexpected technical quality possibilities of the device itself, as well as coding strategies, which further enable improved patients' rehabilitation results. Nevertheless, in spite of cochlear implantation becoming a routine surgical procedure, which has been changing lives of thousands of profoundly deaf adults and children, it has possible complications. Though rare, these complications could lead to severe, even fatal consequences. Bacterial meningitis represents one of the most severe postoperative complications. In this article, our five-year experience with cochlear implantation is shown, compared to other, much bigger, experiences. Despite severity and a potentially fatal outcome of meningitis, it has rarely been seen, and the precise connection between surgical procedure and this complication is not yet clear. Do cochlear implants increase the risk of bacterial meningitis? Are deafness-associated factors predisposing the bacterial meningitis occurrence, independently from the implant? These are the questions that the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA) and the CI surgeons have been facing, as well as manufacturers and patients with their families.

Encapsulation of guests within a gated molecular basket: thermodynamics and selectivity.

Molecular basket 1 has been designed to contain a set of aromatic gates, each with rotational mobility restricted via intramolecular hydrogen bonding. This structural, yet dynamic, feature of the host has been revealed to permit the formation of a transient enclosed space capable of containing haloalkanes, whose size/shape, electronic and entropic attributes contributed to the thermodynamics of binding. Markedly, the basket is capable of mediating the trafficking of a broad range of molecules.

Conversion of perhydropolysilazane into a SiOx network triggered by vacuum ultraviolet irradiation: access to flexible, transparent barrier coatings.

The photochemical conversion of 200-500 nm layers of perhydropolysilazane --(SiH2-NH)n-- (PHPS) in the presence of oxygen into an SiOx network was studied. Different UV sources in the wavelength range of 160-240 nm, that is, 172 nm Xe2* and 222 nm KrCl* excimer, and 185 nm Hg low-pressure (HgLP) lamps were used for these purposes. The role of both ozone and O(1D) as well as of catalytic amounts of tertiary amines in the degradation process of PHPS and the formation of SiOx were studied. In this context, the kinetics of the entire reaction were elucidated and allowed both a continuous and discontinuous process to be established for the production of fully transparent, flexible barrier coatings. Barrier improvement factors (BIFs) of 400 were achieved with one single layer on 23 microm poly(ethyleneterephthalate) (PET), which translated into oxygen transmission rates (OTRs) of 0.20 cm3 m(-2) day(-1) bar(-1). Double layers prepared by this technique allowed the realization of OTRs of or=800.

[Complications of cochlear implant surgery]. / Komplikacije hirurgije kohlearne implantacije.

During the last several decades, cochlear implant has been fully recognized in treatment of severe hearing loss. Development of modern technology enabled inconceivable possibilities of technical qualities of the device as well as development of usable coding strategies, which led to extraordinary results in patient rehabilitation. Although cochlear implantation has become one of the routine operative procedures throughout the world nowadays, it gives rise to certain complications. These complications, though rare, can sometimes be very serious, even with fatal outcome. If cochlear implantation is performed by experienced and well-educated team of experts, the possibility of complications is minimal and is certainly not the argument against cochlear implantation as a method of treatment of severe hearing impairments.

[Cochlear implant application with postlingually deaf patients]. / Primena kohlearnog implanta kod bolesnika sa postlingvalnom gluvocom.

Through last several decades, cochlear implant has been fully recognized for treatment of profound hearing loss. Modern technology development enabled unimagined possibilities in technical qualities of the device, as well as development of usable coding strategies, which led to extraordinary results of patient rehabilitation. It is well known that postlingually deaf implanted patients show better results than prelingually deaf implanted patients. This is to be understood, concerning the fact of matured hearing paths and centers of CNS, presence of developed speech in patients postlingually deaf, contrary to prelingually deaf patients in whom the development of hearing paths and centers is yet to be established only after cochlear implantation. Accordingly, this is a case report of male adult patient B.D. who was implanted because of complete deafness following the application of gentamicin. The results of implantation were excellent and fully justified the choice of the patient for CI application.