ANALYSIS OF THE EDGE EFFECT OF SHEAR STRESSES IN THE SHIFT OF A TWO-LAYER BEAM

The paper presents a system of resolving equations describing the stress-strain state of multilayer beams and allowing solving a wide range of problems, such as shear, bending, and normal separation for any number of layers. For each of the layers, hypotheses similar to the Kirchhoff - Love hypotheses are introduced. In the proposed model, the layers interact with a contact layer. The contact layer is an anisotropic medium, which can be considered as a “brush” of elastic short rods. For simplicity, it is assumed that the rods are oriented normally to the contact surface. The use of a contact layer allows such problems as infinite tangential stresses at the interface between the layers near the end of the beam and also to solve the problem of determining the concentration of the shearing stresses occurring at the boundaries between the layers and in the corner points, their variation, for example, in the creep process. The main feature of the proposed model is strict satisfaction of the boundary conditions. In view of the complexity of the resolving system of equations, we consider, as an example, the problem of shearing the layers of a double-layer beam. An analytical solution is obtained that allows qualitative analysis of the influence of mechanical and geometric characteristics on the stress-strain state of the design model, calculate the true adhesive strength, and determine the physical characteristics of the contact layer on the basis of experimental data. A numerical example is given for calculating a beam in two variants of model loading, on the basis of which a relationship was established between the true and average adhesive strength, depending on various parameters

Nanomesh aluminum films for LC alignment : theoretical and experimental modeling

A porous system for LC alignment is reviewed. Fabrication of nanomesh aluminum films and their porous structure are described. Methods of the nanomesh parameters for optimal LC alignment are discussed. A model of the LC alignment in a porous system is proposed. The LC orientation type is determined by the free anchoring energy and the micropore diameter. The difference between planar and homeotropic anchoring energies appears to be lower than the interaction energy by two orders of magnitude

Topoisomer Differentiation of Molecular Knots by FTICR MS: Lessons from Class II Lasso Peptides

Lasso peptides constitute a class of bioactive peptides sharing a knotted structure where the C-terminal tail of the peptide is threaded through and trapped within an N-terminalmacrolactamring. The structural characterization of lasso structures and differentiation from their unthreaded topoisomers is not trivial and generally requires the use of complementary biochemical and spectroscopic methods. Here we investigated two antimicrobial peptides belonging to the class II lasso peptide family and their corresponding unthreaded topoisomers: microcin J25 (MccJ25), which is known to yield two-peptide product ions specific of the lasso structure under collisioninduced dissociation (CID), and capistruin, for which CID does not permit to unambiguously assign the lasso structure. The two pairs of topoisomers were analyzed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR MS) upon CID, infrared multiple photon dissociation (IRMPD), and electron capture dissociation (ECD). CID and ECDspectra clearly permitted to differentiate MccJ25 from its non-lasso topoisomer MccJ25-Icm, while for capistruin, only ECD was informative and showed different extent of hydrogen migration (formation of c\bullet/z from c/z\bullet) for the threaded and unthreaded topoisomers. The ECD spectra of the triply-charged MccJ25 and MccJ25-lcm showed a series of radical b-type product ions {\eth}b0In{\TH}. We proposed that these ions are specific of cyclic-branched peptides and result from a dual c/z\bullet and y/b dissociation, in the ring and in the tail, respectively. This work shows the potentiality of ECD for structural characterization of peptide topoisomers, as well as the effect of conformation on hydrogen migration subsequent to electron capture

Drug-to-Antibody Ratio Estimation via Proteoform Peak Integration in the Analysis of Antibody-Oligonucleotide Conjugates with Orbitrap Fourier Transform Mass Spectrometry

The therapeutic efficacy and pharmacokinetics of antibody-drug conjugates (ADCs) in general, and antibody-oligonucleotide conjugates (AOCs) in particular, depend on the drug-to-antibody ratio (DAR) distribution and average value. The DAR is considered a critical quality attribute, and information pertaining to it needs to be gathered during ADC/AOC development, production, and storage. However, because of the high structural complexity of ADC/AOC samples, particularly in the initial drug-development stages, the application of the current state-of-the-art mass spectrometric approaches can be limited for DAR analysis. Here, we demonstrate a novel approach for the analysis of complex ADC/AOC samples, following native size-exclusion chromatography Orbitrap Fourier transform mass spectrometry (FTMS). The approach is based on the integration of the proteoform-level mass spectral peaks in order to provide an estimate of the DAR distribution and its average value with less than 10% error. The peak integration is performed via a truncation of the Orbitrap's unreduced time-domain ion signals (transients) before mass spectra generation via FT processing. Transient recording and processing are undertaken using an external data acquisition system, FTMS Booster X2, coupled to a Q Exactive HF Orbitrap FTMS instrument. This approach has been applied to the analysis of whole and subunit-level trastuzumab conjugates with oligonucleotides. The obtained results indicate that ADC/AOC sample purification or simplification procedures, for example, deglycosylation, could be omitted or minimized prior to the DAR analysis, streamlining the drug-development process