Molecular Force Research Articles

Bionic Engineered Protein Coating Boosting Anti-Biofouling in Complex Biological Fluids.

Implantable medical devices have been widely applied in diagnostics, therapeutics, organ restoration, and other biomedical areas, but often suffer from dysfunction and infections due to irreversible biofouling. Inspired by the self-defensive "vine-thorn" structure of climbing thorny plants, a zwitterion-conjugated protein is engineered via grafting sulfobetaine methacrylate (SBMA) segments on native bovine serum albumin (BSA) protein molecules for surface coating and antifouling applications in complex biological fluids. Unlike traditional synthetic polymers of which the coating operation requires arduous surface pretreatments, the engineered protein BSA@PSBMA (PolySBMA conjugated BSA) can achieve facile and surface-independent coating on various substrates through a simple dipping/spraying method. Interfacial molecular force measurements and adsorption tests demonstrate that the substrate-foulant attraction is significantly suppressed due to strong interfacial hydration and steric repulsion of the bionic structure of BSA@PSBMA, enabling coating surfaces to exhibit superior resistance to biofouling for a broad spectrum of species including proteins, metabolites, cells, and biofluids under various biological conditions. This work provides an innovative paradigm of using native proteins to generate engineered proteins with extraordinary antifouling capability and desired surface properties for bioengineering applications.

Analysis of Visual Characteristics of Short-circuited Arc Sites

Identifying the cause of fire at a fire site is an important fire prevention measure to prevent recurrence. In particular, information about molten marks of the copper wire is essential to check whether electric power is being supplied at the fire site. This study aims to analyse the visual characteristics of arc sites formed by a short circuit to identify the molten marks at the fire site. When a short circuit occurs, electromagnetic force is generated by the short circuit current, and the arc repulsion force is generated by the contact arc. In this study, the effects of the forces, which act on the short-circuited melted area, on the formation of copper molten marks were investigated. Copper molten marks formed by a short circuit were experimentally fabricated, and the visual characteristics based on the force that was applied to the melted area were identified and classified based on features. The results showed that the melted area was affected by both the arc repulsion and electromagnetic forces, resulting in the visual differences between the short-circuited arc sites and flame-melted ones, which are affected by gravity and molecular force. These results provide a theoretical basis for discriminating between arc sites formed by a short circuit and flame-melted marks at the fire site. The validity of this study was verified via a comparative analysis using shape and cross-sectional microstructure of molten marks collected at the fire site.

Insights into the trace Sr2+ impact on the gel properties and spatial structure of mutton myofibrillar proteins

Myofibrillar proteins (MPs) and the quality of meat strongly depend on the properties of MP gels, which in turn depend on several parameters that include the thermal history and the concentration of metal ions. Strontium element (Sr) widely exists in mineral water and is found as strontium ions (Sr2+), which is an essential trace element for humans. This study investigated the effects of trace Sr2+ on the structure–function relationship of mutton MPs, as well as their gels with water. Trace concentrations of Sr2+ were found to significantly alter the conformation of the MPs. An increase in Sr2+ concentration was associated with a reduction in the tightness and strength of the gel and a significant increase in its water-holding capacity As compared to the untreated control sample, the solubility, particle size, and the magnitude of the Zeta potential of the gels increased by 13.03 %, 12.62 %, and 19.73 %, respectively, whereas the water retention capacity and the gel strength increased by 23.13 % and 21.90 %, at a Sr2+ concentration of 5.0 mg/L. Molecular docking predicted an increase in ionic bonds and disulfide bonds because Sr2+ had a strong interaction with hydrophilic amino acids and acidic amino acids. The analysis of molecular forces further verified the significant facilitation of interactions between MP molecules with the induction of Sr2+. As compare to the untreated control group, the ionic and disulfide bonds increased by 141.17 % and 66.94 %, when treated with 5.0 mg/L Sr2+. These changes were likely due to the enhancement of protein–protein interactions caused by Sr2+, which could induce MP molecules to properly unfold and aggregate in gel formation. The results could provide a basis for improving the texture and the quality of meat and meat products.

Mechanical DNA Origami to Investigate Biological Systems.

The ability to self-assemble DNA nanodevices with programmed structural dynamics that can sense and respond to the local environment can enable transformative applications in fields including mechanobiology and nanomedicine. The responsive function of biomolecules is often driven by alterations in conformational distributions mediated by highly sensitive interactions with the local environment. In this review, the current state-of-the-art in constructing complex DNA geometries with dynamic and mechanical properties to enable a molecular scale force measurement is first summarized. Next, an overview of engineering modular DNA devices that interact with cell surfaces is highlighted detailing examples of mechanosensitive proteins and the force-induced dynamic molecular interaction on the downstream biochemical signaling. Finally, the challenges and an outlook on this promising class of DNA devices acting as nanomachines to operate at a low piconewton range suitable for a majority of biological effects or as hybrid materials to achieve higher tension exertion required for other biological investigations, are discussed.

Теоретическое и экспериментальное обоснование характера взаимодействия модифицированных связующих с древесиной

There are numerous methods for analyzing surface phenomena when bonding wood materials, mutual arrangement of pores in the wood substrate, and depth of liquid adhesive penetration into wood. Electron microscopic methods such as atomic force and scanning tunneling microscopy are used along with optical methods. They allow evaluating the influence of factors describing the interaction between the liquid adhesive molecules and the porous wood surface. Phenol formaldehyde resin modified with pectol and urea formaldehyde resin modified with lignosulfonates were used for substantiation of the interaction mechanism between modified adhesives and wood. Electron microscopy was used to study the depth of adhesive penetration into veneer. The plywood was produced using modified urea and phenol formaldehyde adhesives. After conditioning, samples with a thickness of 0.025 mm were cut out and examined with a scanning electron microscope. The article shows that the interaction between liquid phenol formaldehyde adhesive modified with pectol and wood results in a sequential increase in the molecular weight of the substances and, consequently, in the penetration degree (depth). The studied wood species (birch, pine and larch) and modified thermosetting urea and phenol formaldehyde adhesives are polar materials (adhesive interacts with wood molecules with the formation of intermolecular bonds, including hydrogen bonds). The molecular weight growth and the freely joined nature of the main chain (liquid modified adhesive macromolecules), which contains a large number of polar functional groups (adhesive and wood), promote intermolecular association. The formation of an adhesive bond between urea formaldehyde adhesive modified with lignosulfonates and wood occurs due to chemical interaction between hydroxyl groups of cellulose macromolecules and methoxyl groups of urea resin with the formation of esters (hydrogen atoms of hydroxyl groups OH are substituted with hydrocarbon radicals R). The formation of a bond between the adhesive and the wood surface is the result of molecular interaction forces at the liquid adhesive – wood interface, when the distance between molecules of the same polarity (adhesive and wood) is less than 0.5 nm. Then, adsorption equilibrium sets in. For citation: Rusakov D.S., Varankina G.S., Chubinsky A.N. Theoretical and Experimental Substantiation of the Nature of Interaction between Modified Binders and Wood. Lesnoy Zhurnal = Russian Forestry Journal, 2022, no. 6, pp. 153–163. (In Russ.). https://doi.org/10.37482/0536-1036-2022-6-153-163

Effect of citrus fiber on the phosphate-mediated gel properties of myofibrillar protein and partial replacement of phosphate

To evaluate the effect of citrus fiber (CF) on the phosphate-mediated gel properties of myofibrillar protein (MP) and partial replacement of phosphate, gels properties, emulsifying properties, molecular forces and structural characteristics, water distributions, microstructure of MP composite gels with sodium tripolyphosphate (STP) and CF were investigated. The results showed that the addition of STP and CF could enhance the gel properties by unfolding the structure of α-helix, and increasing the hydrophobic interactions and hydrogen bonds, which were the primary molecular forces to stabilize the structure of MP-STP-CF composite gels. The measurement of relaxation time and microstructure further verified that STP and CF could convert more free water into immobile water, forming a more stable three-dimensional network structure. MP gel added with 5% STP and 10% CF exhibited the best gel properties, but excessive CF addition would weaken the intermolecular forces and immobile water content, then destroyed the gel properties. Moreover, MP gel with 3% STP and 10% CF addition had no significant difference on the gel properties and structures compared with MP gel with 5% STP. The results provided basic theoretical support for the application of CF in improving the structure of meat products and the partial substitution of phosphate.

How does dextran sulfate promote the egg white protein to form transparent hydrogel?the gelation mechanism and molecular force changes

Most globular protein solutions will form turbid gels when heated and exhibit unsatisfactory mechanical strength. Our previous study found that highly charged dextran sulfate (DS) has the potential to induce egg white protein (EWP) to form transparent hydrogel with excellent gelation properties. However, the mechanism is not clear. Therefore, the effect of DS on the gelation characteristics of EWP was investigated, including rheological properties, microstructures, water distributions, molecule conformation, and intermolecular forces. Results showed that DS addition significantly prevented the formation of large insoluble aggregates of EWP during heating, which is the prerequisite for forming a transparent gel. The EWP/DS hydrogel possesses remarkably higher gel strength and water holding capacity compared to EWP. The microstructure analysis showed that EWP/DS has a highly ordered fibrous mesh structure after heat treatment. Fourier transform infrared spectroscopy (FT-IR) revealed that DS addition promotes the denaturation of EWP (decrease in α-helices and increase in β-sheets). In addition, hydrophobic interactions are confirmed to be the major intermolecular force in EWP/DS, rather than disulfide bonds in EWP and EWP/dextran gels. Overall, combining the data from turbidity, FT-IR, and microstructure analysis, we found that the EWP/DS complex formation effectively suppresses the further disordered aggregation process of denatured protein by electrostatic repulsion. This work will be beneficial to understand the mechanism of DS on the gelation of EWP after thermal treatment, which will expand the application of sulfated polysaccharides on food structure design. • Dextran sulfate (DS) addition induced egg white protein (EWP) to form a transparent hydrogel under heat treatment. • The EWP/DS composite hydrogel possesses excellent gelation properties compared to that of the native EWP. • The improvement was largely due to high electrostatic repulsion of EWP/DS coacervates which suppress the formation of insoluble protein aggregates. • Hydrophobic interactions were the major intermolecular force in EWP/DS composite hydrogel.

Molecular mechanics simulations of lattice dynamical properties of the spin crossover complex [Fe(pyrazine)][Ni(CN)4

An empirical molecular mechanics force field has been built for the [Fe(pyrazine)][Ni(CN)4] spin crossover complex using Raman spectroscopic and nuclear inelastic scattering data. Based on this force field, molecular dynamics simulations were conducted to investigate the lattice dynamical properties of the complex in the high-spin and low-spin states. The extracted thermodynamic and mechanical parameters match well with the corresponding experimental data. Most importantly, the force field can successfully reproduce the low-frequency acoustic part of the partial densities of vibrational states, which is vital for the understanding the thermodynamic analysis of the spin crossover phenomenon in crystalline solids and which would be difficult to tackle by quantum mechanical methods.

The effect of heating method on the gel structures and properties of surimi prepared from Bombay duck (Harpadon nehereus).

This study investigates the effects of heating method, setting time, and setting temperature on the gel properties, water holding capacity (WHC), molecular forces, protein composition, protein conformation, and water transition of Bombay duck (BD) surimi gel. The obtained results demonstrate that the best gel properties are obtained by two-step heating at 30°C for 120 min while the hardness was 10.418 N and the breaking force was 4.52 N. Gel softening occurs at setting temperatures greater than 40°C due to the effect of endogenous enzymes in destroying the protein structure and increasing the hydrophobic and disulfide interactions. Low-field nuclear magnetic resonance spectra confirm that high two-step setting temperatures induce gel softening and the destruction of the surimi gel structure, as evidenced by the increased water migration at these temperatures. Of all protein conformations in the gel, the β-sheet structure, decreases from 38.40% at 30°C to 11.75% at 60°C when the setting time is 60 min, is the most susceptible to gel softening. Overall, the data reported herein provide a scientific basis for the development of new BD surimi products on an industrial level.

Enhancing Biomolecular Simulations with Hybrid Potentials Incorporating NMR Data.

Some recent advances in biomolecular simulation and global optimization have used hybrid restraint potentials, where harmonic restraints that penalize conformations inconsistent with experimental data are combined with molecular mechanics force fields. These hybrid potentials can be used to improve the performance of molecular dynamics, structure prediction, energy landscape sampling, and other computational methods that rely on the accuracy of the underlying force field. Here, we develop a hybrid restraint potential based on NapShift, an artificial neural network trained to predict protein nuclear magnetic resonance (NMR) chemical shifts from sequence and structure. In addition to providing accurate predictions of experimental chemical shifts, NapShift is fully differentiable with respect to atomic coordinates, which allows us to use it for structural refinement. By employing NapShift to predict chemical shifts from the protein conformation at each simulation step, we can compute an energy penalty and the corresponding hybrid restraint forces based on the difference between the predicted values and the experimental chemical shifts. The performance of the hybrid restraint potential was benchmarked using both basin-hopping global optimization and molecular dynamics simulations. In each case, the NapShift hybrid potential improved the accuracy, leading to better structure prediction via basin-hopping and increased local stability in molecular dynamics simulations. Our results suggest that neural network hybrid potentials based on NMR observables can enhance a broad range of molecular simulation methods, and the prediction accuracy will improve as more experimental training data become available.

Application of seaweed dietary fiber as a potential alternative to phosphates in frankfurters with healthier profiles

This study was designed to investigate the utilization of seaweed dietary fiber (SDF) as a potential alternative to phosphates on the quality profiles of phosphate-free frankfurters. The results showed that the incorporation of SDF obviously promote the textural parameters of phosphate-free frankfurters, which was effectively verified by scanning electron microscopy. Meanwhile, SDF effectively retarded lipid oxidation of phosphate-free frankfurters during storage (P < 0.05). Moreover, 1.00% SDF was proven to show the best optimal phosphates replacing effect, as well as overcome the quality defects of phosphate-free frankfurters to the maximum extent. In addition, hydrogen bonding and hydrophobic interactions were the primary molecular force in SDF-added phosphate-free frankfurters. Therefore, our results implied that SDF can be considered as a feasible alternative for the processing of phosphate-free frankfurters with improved quality profile and superior health benefits which consistent with the demand of healthier meat products.

Letting go: Dishevelled phase separation recruits Axin to stabilize β-catenin.

Dishevelled exerts a molecular force that guides cell fate, but how it does so remains enigmatic. In this issue, Kang et al. (2022. J. Cell Biol.https://doi.org/10.1083/jcb.202205069) show Dvl2 undergoes liquid-liquid phase separation to stabilize β-catenin by pulling Axin into its biomolecular condensate at the plasma membrane.

Structural evolution in Au- and Pd-based metallic glass forming liquids and the case for improved molecular dynamics force fields.

The results of a combined experimental and computational investigation of the structural evolution of Au81Si19, Pd82Si18, and Pd77Cu6Si17 metallic glass forming liquids are presented. Electrostatically levitated metallic liquids are prepared, and synchrotron x-ray scattering studies are combined with embedded atom method molecular dynamics simulations to probe the distribution of relevant structural units. Metal-metalloid based metallic glass forming systems are an extremely important class of materials with varied glass forming ability and mechanical processibility. High quality experimental x-ray scattering data are in poor agreement with the data from the molecular dynamics simulations, demonstrating the need for improved interatomic potentials. The first peak in the x-ray static structure factor in Pd77Cu6Si17 displays evidence for a Curie-Weiss type behavior but also a peak in the effective Curie temperature. A proposed order parameter distinguishing glass forming ability, 1/ST,q1-1, shows a peak in the effective Curie temperature near a crossover temperature established by the behavior of the viscosity, TA.

Noscapine-Amino Acid Conjugates Suppress the Progression of Cancer Cells.

Lung cancer is the leading cause of cancer deaths globally; 1 in 16 people are diagnosed with lung cancer in their lifetime. Microtubules, a critical cytoskeletal assembly, have an essential role in cell division. Interference with the microtubule assembly leads to genetic instability during mitosis and cancer cell death. Currently, available antimitotic drugs such as vincas and taxanes are limited due to side effects such as alopecia, myelosuppression, and drug resistance. Noscapine, an opium alkaloid, is a tubulin-binding agent and can alter the microtubule assembly, causing cancer cell death. Amino acids are fundamental building blocks for protein synthesis, making them essential for the biosynthesis of cancer cells. However, the ability of amino acids in drug transportation has yet to be exploited in developing noscapine analogues as a potential drug candidate for cancer. Hence, in the present study, we have explored the ninth position of noscapine by introducing a hydroxymethylene group using the Blanc reaction and further coupled it with a series of amino acids to construct five target conjugates in good yields. The synthesized amino acid conjugate molecules were biologically evaluated against the A549 lung cancer cell line, among which the noscapine-tryptophan conjugate showed IC50 = 32 μM, as compared to noscapine alone (IC50 = 73 μM). Morphological changes in cancer cells, cell cycle arrest in the G1 phase, and ethidium bromide/acridine orange staining indicated promising anticancer properties. Molecular docking confirmed strong binding to tubulin, with a score of -41.47 kJ/mol with all 3D coordinates and significant involvement of molecular forces, including the hydrogen bonds and hydrophobic interactions. Molecular dynamics simulations demonstrated a stable binding of noscapine-tryptophan conjugate for a prolonged time (100 ns) with the involvement of free energy through the reaction coordinates analyses, solving the bioavailability of parent noscapine to the body.

Low cost and massively parallel force spectroscopy with fluid loading on a chip

Current approaches for single molecule force spectroscopy are typically constrained by low throughput and high instrumentation cost. Herein, a low-cost, high throughput technique is demonstrated using microfluidics for multiplexed mechanical manipulation of up to ~4000 individual molecules via molecular fluid loading on-a-chip (FLO-Chip). The FLO-Chip consists of serially connected microchannels with varying width, allowing for simultaneous testing at multiple loading rates. Molecular force measurements are demonstrated by dissociating Biotin-Streptavidin and Digoxigenin-AntiDigoxigenin interactions along with unzipping of double stranded DNA of varying sequence under different dynamic loading rates and solution conditions. Rupture force results under varying loading rates and solution conditions are in good agreement with prior studies, verifying a versatile approach for single molecule biophysics and molecular mechanobiology. FLO-Chip enables straightforward, rapid, low-cost, and portable mechanical testing of single molecules that can be implemented on a wide range of microscopes to broaden access and may enable new applications of molecular force spectroscopy.

Impacts of soybean protein isolate hydrolysates produced at high hydrostatic pressure on gelling properties, structural characteristics, and molecular forces of myofibrillar protein.

Soybean protein isolate hydrolysates (SPIHs) produced at high hydrostatic pressure have higher bioactivity. The aim of the study was to analyze the effects of different SPIH concentrations obtained under various pressures (0.1, 100, 200, and 300 MPa) on gelling properties, structural characteristics, and main forces of myofibrillar protein (MP) in MP-SPIH plural gels. The MP-SPIH plural gel with 3% SPIH produced under 200 MPa had the maximum gel strength (0.42 N) and water holding capacity (53.69%). A decline in thermal stability and a rise in storage modulus (G') of MP-SPIH plural gels were found with increased SPIH pressure and concentration. Additionally, the addition of SPIHs increased the amounts of α-helix and β-sheet, decreased random coil structural content of MP in MP-SPIH plural gels, and facilitated the generation of a denser and uniform gels network. The molecular forces in MP-SPIH plural gels were mainly hydrophobic interaction and hydrogen bond. This study showed that the interaction of MP with 3% SPIH obtained at 200 MPa improved the quality of plural gels. © 2022 Society of Chemical Industry.

Plastic bending in a semiconducting coordination polymer crystal enabled by delamination

Coordination polymers (CPs) are a class of crystalline solids that are considered brittle, due to the dominance of directional coordination bonding, which limits their utility in flexible electronics and wearable devices. Hence, engineering plasticity into functional CPs is of great importance. Here, we report plastic bending of a semiconducting CP crystal, Cu-Trz (Trz = 1,2,3-triazolate), that originates from delamination facilitated by the discrete bonding interactions along different crystallographic directions in the lattice. The coexistence of strong coordination bonds and weak supramolecular interactions, together with the unique molecular packing, are the structural features that enable the mechanical flexibility and anisotropic response. The spatially resolved analysis of short-range molecular forces reveals that the strong coordination bonds, and the adaptive C–H···π and Cu···Cu interactions, synergistically lead to the delamination of the local structures and consequently the associated mechanical bending. The proposed delamination mechanism offers a versatile tool for designing the plasticity of CPs and other molecular crystals.

Combined 3D-QSAR, molecular docking and dynamics simulations studies to model and design TTK inhibitors.

Tyrosine threonine kinase (TTK) is the key component of the spindle assembly checkpoint (SAC) that ensures correct attachment of chromosomes to the mitotic spindle and thereby their precise segregation into daughter cells by phosphorylating specific substrate proteins. The overexpression of TTK has been associated with various human malignancies, including breast, colorectal and thyroid carcinomas. TTK has been validated as a target for drug development, and several TTK inhibitors have been discovered. In this study, ligand and structure-based alignment as well as various partial charge models were used to perform 3D-QSAR modelling on 1H-Pyrrolo[3,2-c] pyridine core containing reported inhibitors of TTK protein using the comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) approaches to design better active compounds. Different statistical methods i.e., correlation coefficient of non-cross validation (r2), correlation coefficient of leave-one-out cross-validation (q2), Fisher's test (F) and bootstrapping were used to validate the developed models. Out of several charge models and alignment-based approaches, Merck Molecular Force Field (MMFF94) charges using structure-based alignment yielded highly predictive CoMFA (q2 = 0.583, Predr2 = 0.751) and CoMSIA (q2 = 0.690, Predr2 = 0.767) models. The models exhibited that electrostatic, steric, HBA, HBD, and hydrophobic fields play a key role in structure activity relationship of these compounds. Using the contour maps information of the best predictive model, new compounds were designed and docked at the TTK active site to predict their plausible binding modes. The structural stability of the TTK complexes with new compounds was confirmed using MD simulations. The simulation studies revealed that all compounds formed stable complexes. Similarly, MM/PBSA method based free energy calculations showed that these compounds bind with reasonably good affinity to the TTK protein. Overall molecular modelling results suggest that newly designed compounds can act as lead compounds for the optimization of TTK inhibitors.

Probing the Interfacial Forces and Surface Interaction Mechanisms in Petroleum Production Processes

Despite the advances that have been made in renewable energy over the past decade, crude oil or petroleum remains one of the most important energy resources to the world. Petroleum production presents many challenging issues, such as the destabilization of complex oil–water emulsions, fouling phenomena on pipelines and other facilities, and water treatment. These problems are influenced by the molecular forces at the oil/water/solid/gas interfaces involved in relevant processes. Herein, we present an overview of recent advances on probing the interfacial forces in several petroleum production processes (e.g., bitumen extraction, emulsion stabilization and destabilization, fouling and antifouling phenomena, and water treatment) by applying nanomechanical measurement technologies such as a surface forces apparatus (SFA) and an atomic force microscope (AFM). The interaction forces between bitumen and mineral solids or air bubbles in the surrounding fluid media determine the bitumen liberation and flotation efficiency in oil sands production. The stability of complex oil/water emulsions is governed by the forces between emulsion drops and particularly between interface-active species (e.g., asphaltenes). Various oil components (e.g., asphaltenes) and emulsion drops interact with different substrate surfaces (e.g., pipelines or membranes), influencing fouling phenomena, oil–water separation, and wastewater treatment. Quantifying these intermolecular and interfacial forces has advanced the mechanistic understanding of these interfacial interactions, facilitating the development of advanced materials and technologies to solve relevant challenging issues and improve petroleum production processes. Remaining challenges and suggestions on future research directions in the field are also presented.

The staphylococcal biofilm protein Aap mediates cell-cell adhesion through mechanically distinct homophilic and lectin interactions.

The accumulation phase of staphylococcal biofilms relies on both the production of an extracellular polysaccharide matrix and the expression of bacterial surface proteins. A prototypical example of such adhesive proteins is the long multidomain protein Aap (accumulation-associated protein) from Staphylococcus epidermidis, which mediates zinc-dependent homophilic interactions between Aap B-repeat regions through molecular forces that have not been investigated yet. Here, we unravel the remarkable mechanical strength of single Aap-Aap homophilic bonds between living bacteria and we demonstrate that intercellular adhesion also involves sugar binding through the lectin domain of the Aap A region. We find that the mechanical force needed to unfold individual β-sheet-rich G5-E domains from the Aap B-repeat regions is very high, ranging from 300 up to 1,000 pN at high loading rates, indicating these are extremely stable. This high mechanostability provides a means to the cells to form highly adhesive and cohesive biofilms capable of sustaining high physiological shear stress. Importantly, we identify a previously undescribed role of Aap in bacterial-bacterial adhesion, that is, heterophilic sugar binding by a specific lectin domain located in the N-terminal A region, which might be important to establish initial contacts between cells before strong homophilic bonds come into play. This study emphasizes the remarkable mechanical and binding properties of Aap as well as its wide diversity of adhesive functions.