CYP154C5 Regioselectivity in Steroid Hydroxylation Explored by Substrate Modifications and Protein Engineering**

CYP154C5 from Nocardia farcinica is a P450 monooxygenase able to hydroxylate a range of steroids with high regio- and stereoselectivity at the 16α-position. Using protein engineering and substrate modifications based on the crystal structure of CYP154C5, an altered regioselectivity of the enzyme in steroid hydroxylation had been achieved. Thus, conversion of progesterone by mutant CYP154C5 F92A resulted in formation of the corresponding 21-hydroxylated product 11-deoxycorticosterone in addition to 16α-hydroxylation. Using MD simulation, this altered regioselectivity appeared to result from an alternative binding mode of the steroid in the active site of mutant F92A. MD simulation further suggested that the entrance of water to the active site caused higher uncoupling in this mutant. Moreover, exclusive 15α-hydroxylation was observed for wild-type CYP154C5 in the conversion of 5α-androstan-3-one, lacking an oxy-functional group at C17. Overall, our data give valuable insight into the structure–function relationship of this cytochrome P450 monooxygenase for steroid hydroxylation.     

Modeling of the Formation of Steep Portions of a Piecewise Continuous Profile in a One-Step Technology for Fabricating Diffractive Optical Elements using Oblique Laser Beams

This paper presents the results of modeling the most important component of a one-step technology of fabricating kinoform lenses in thick photoresist layers with increased diffraction efficiency due to the formation of backward slopes of Fresnel zones with a steepness of up to 90° using oblique laser beams. It is shown that this method of fabricating volume structures makes it possible to significantly increase the steepness of backward slopes of the zones in low-contrast photoresists (k = 3) and to form practically vertical slopes in moderate-contrast photoresists (k = 10).     

Better and Simpler Approximation Algorithms for?the?Stable Marriage Problem

We first consider the problem of finding a maximum size stable matching if incomplete lists and ties are both allowed, but ties are on one side only. For this problem we give a simple, linear time 3/2-approximation algorithm, improving on the best known approximation factor 5/3 of Irving and Manlove (J. Comb. Optim., doi:10.1007/s10878-007-9133-x, 2007). Next, we show how this extends to the Hospitals/Residents problem with the same ratio if the residents have strict orders. We also give a simple linear time algorithm for the general problem with approximation factor 5/3, improving the best known 15/8-approximation algorithm of Iwama, Miyazaki and Yamauchi (SODA ??07: Proceedings of the Eighteenth Annual ACM-SIAM Symposium on Discrete Algorithms, pp.?288?C297, 2007). For the cases considered in this paper it is NP-hard to approximate within a factor of 21/19 by the result of Halldórsson et?al. (ACM Transactions on Algorithms 3(3):30, 2007). Our algorithms not only give better approximation ratios than the cited ones, but are much simpler and run significantly faster. Also we may drop a restriction used in (J. Comb. Optim., doi:10.1007/s10878-007-9133-x, 2007) and the analysis is substantially more moderate. Preliminary versions of this paper appeared in (Király, Egres Technical Report TR-2008-04, www.cs.elte.hu/egres/, 2008; Király in Proceedings of MATCH-UP 2008: Matching Under Preferences??Algorithms and Complexity, Satellite Workshop of ICALP, July 6, 2008, Reykjavík, Iceland, pp.?36?C45, 2008; Király in ESA 2008, Lecture Notes in Computer Science, vol.?5193, pp.?623?C634, 2008). For the related results obtained thenceforth see Sect.?5.     

A method to estimate efficiency of the connection control mechanisms in wireless self-organizing networks

An original method to estimate efficiency of the algorithms for opening and closing links in the wireless self-organizing networks (mesh networks) was proposed. It can be used to develop a mathematical model of the algorithm standardized in the mesh network specification IEEE 802.11s. The proposed method was shown to be sufficiently general and applicable to developing the models of other link management algorithms.     

Transport of Cu(II) ions through charged cation‐exchange membranes

Transport of Cu(II) ions through polysulfonated cation‐exchange membranes under Donnan dialysis conditions was studied as a function of the pH gradient. The used charged membranes are homogeneous (polysulfone composition) and heterogeneous (polysulfone with polyester support) structures which are strongly acidic cation‐exchange microporous‐type membranes. The flux increases with decreasing of the pH gradient, which is influenced by the transport of copper ions. The quantitative relations were obtained which describe the time dependence of the transport system with the equilibrium distribution and the results were correlated with the flux data as well as with the membrane structure. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 421–427, 2001     

Syndecan-4 Is a Key Facilitator of the SARS-CoV-2 Delta Variant’s Superior Transmission

Emerging SARS-CoV-2 variants pose threats to vaccination campaigns against COVID-19. Being more transmissible than the original virus, the SARS-CoV-2 B.1.617 lineage, named the Delta variant, swept through the world in 2021. The mutations in the Delta’s spike protein shift the protein towards a net positive electrostatic potential. To understand the key molecular drivers of the Delta infection, we investigate the cellular uptake of the Delta spike protein and Delta spike-bearing SARS-CoV-2 pseudoviruses. Specific in vitro modification of ACE2 and syndecan expression enabled us to demonstrate that syndecan-4, the syndecan isoform abundant in the lung, enhances the transmission of the Delta variant by attaching its mutated spike glycoprotein and facilitating its cellular entry. Compared to the wild-type spike, the Delta one shows a higher affinity towards heparan sulfate proteoglycans than towards ACE2. In addition to attachment to the polyanionic heparan sulfate chains, the Delta spike’s molecular interactions with syndecan-4 also involve syndecan-4’s cell-binding domain that mediates cell-to-cell adhesion. Regardless of the complexity of these interactions, exogenously added heparin blocks Delta’s cellular entry as efficiently as syndecan-4 knockdown. Therefore, a profound understanding of the molecular mechanisms underlying Delta infections enables the development of molecularly targeted yet simple strategies to reduce the Delta variant’s spread.     

Six-layer lamination of a new dry film negative-tone photoresist for fabricating complex 3D microfluidic devices

We present a new epoxy-based negative-tone dry film photoresist (DFR) for fabricating multilayer microfluidic devices using a lamination process combined with a standard photolithography technology. As proof-of-concept, a complex 3D-hydrodynamic focusing device was produced via a six-layer lamination process of 33 µm-thick DFR layers. The bonding strength of the new DFR was tested on silicon, glass, and titanium substrates, respectively. A maximum bonding strength of 37 MPa was obtained for the dry film photoresist laminated on glass. No leakage was found, and burst tests proved excellent robustness and sealing reliability of the microchannels.     

Sorption of pyrene to dissolved humic substances and related model polymers. 2. Solid-phase microextraction (SPME) and fluorescence quenching technique (FHT) as analytical methods

Sorption coefficients for pyrene on dissolved humic substances and on poly(acrylic acid) esters as well-defined model polymers were determined using solid-phase microextraction (SPME) and the fluorescence quenching technique (FQT). The results of both analytical methods were compared and theoretically evaluated, which led to the conclusion that the sorption coefficients measured by SPME and FQT are inevitably different: SPME measures activity-based and FQT concentration-based sorption coefficients. The environmental relevance of the two types of sorption coefficients is discussed. FQT is inappropriate to measure sorption coefficients for pyrene with the synthetic sorbents. Inspection of the vibrational structure of the fluorescence spectra of those solutions indicates a highly hydrophobic microenvironment of pyrene. This can be explained by an intra- or intermolecular agglomeration of hydrophobic moieties forming a favorable host for hydrophobic solutes.     

The possibility of realizing a noncompensation method of measuring the radar characteristics of targets

The effect of electrodynamic interaction between the transmitting and receiving exciters of the collimator of a coherent radar measuring system on the accuracy of measurements of the radar characteristics of targets is estimated. The possibility of improving the decoupling between the exciterss by using radio-absorbing materials is investigated.Translated from Izmeritelnaya Tekhnika, No. 10, pp. 43–46, October, 2004.     

Method of extended bicharacteristic system in simulating wave propagation in ionospheric plasma

A procedure for studying wave propagation in ionospheric plasma based on the use of a bicharacteristic system and an extended bicharacteristic system of equations that allows the caustic structure to be determined has been developed. Propagation of an ordinary and extraordinary waves in an anisotropic plasma, in a one-layer and two-layer models, in the presence of local irregularities, has been numerically simulated. With the use of the radiotomography data, the effect of the equatorial anomaly on the propagation of decameter waves has been investigated.