Internal Secondary Structural Conformational States of Silk Fibroin Studied by Raman Spectroscopy with Band Deconvolution Analysis.

Silk fibroin (SF) is an extensively utilized biofiber recognized for its excellent mechanical properties across various applications. However, the relationship between its internal structure and mechanical behavior remains inadequately understood. In this work, we employed polarized Raman spectra to investigate how SF's secondary structures respond to external tensile loads.

Reexamination of Damping in Sliding Friction.

Friction is responsible for about one-third of the primary energy consumption in the world. So far, a thorough atomistic understanding of the frictional energy dissipation mechanisms is still lacking. The Amontons' law states that kinetic friction is independent of the sliding velocity while the Prandtl-Tomlinson model suggests that damping is proportional to the relative sliding velocity between two contacting objects.

Modulating Friction by the Phase of the Vertical Vibrational Excitation at Washboard Frequency.

Applying external vibrations at the resonant frequencies of the frictional system has been a highly effective approach to suppress friction but usually requires additional energy consumption. In this study, we find that in addition to exerting the vibration at the resonant frequency of the frictional system, the friction force on the atomically flat silicon surface can also present a local minimum when the oscillation frequency of the vertical vibrational excitation equals the washboard frequency with respect to the sliding velocity. Moreover, compared with the additional energy consumption at the resonant frequency, applying vertical vibrational excitation at the washboard frequency requires much less energy consumption.

The quality of life in nasopharyngeal carcinoma radiotherapy: A longitudinal study.

Objective: This article aims to longitudinally compare nasopharyngeal carcinoma (NPC) patients' quality of life (QoL) during radiotherapy (RT) and identify QoL correlates.

Methods: This study included 98 patients, with 85 completing full follow-up. Data were collected at baseline (T), midpoint of RT (T), and RT completion (T), between October 2021 and November 2022.

Navigated Delivery of Peptide to the Nanopore Using In-Plane Heterostructures of MoS and SnS for Protein Sequencing.

The impressive success of DNA sequencing using nanopores makes it possible to realize nanopore based protein sequencing. Well-controlled capture and linear movement of the protein are essential for accurate nanopore protein sequencing. Here, by taking advantage of different binding affinities of protein to two isomorphic materials, we theoretically designed a heterostructual platform for delivering the unfolded peptide to the nanopore sensing region.

Resonance in Atomic-Scale Sliding Friction.

Friction represents a major energy dissipation mode, yet the atomistic mechanism of how friction converts mechanical motion into heat remains elusive. It has been suggested that excess phonons are mainly excited at the washboard frequency, the fundamental frequency at which relative motion excites the interface atoms, and the subsequent thermalization of these nonequilibrium phonons completes the energy dissipation process. Through combined atomic force microscopy measurements and atomistic modeling, here we show that the nonlinear interactions between a sliding tip and the substrate can generate excess phonons at not only the washboard frequency but also its harmonics.

Sequence-Specific Detection of DNA Strands Using a Solid-State Nanopore Assisted by Microbeads.

Simple, rapid, and low-cost detection of DNA with specific sequence is crucial for molecular diagnosis and therapy applications. In this research, the target DNA molecules are bonded to the streptavidin-coated microbeads, after hybridizing with biotinylated probes. A nanopore with a diameter significantly smaller than the microbeads is used to detect DNA molecules through the ionic pulse signals.

Concentration effects on capture rate and translocation configuration of nanopore-based DNA detection.

Nanopore is a kind of powerful tool to detect single molecules and investigate fundamental biological processes. In biological cells or real detection systems, concentration of DNA molecules is various. Here, we report an experimental study of the effects of DNA concentration on capture rate and translocation configuration with different sized nanopores and applied voltages.

Diminishing Cohesion of Chitosan Films in Acidic Solution by Multivalent Metal Cations.

Chitosan is a natural polymer with good biocompatibility, biodegradability, and bioactivity that has great potential for biomedical and industrial applications. Like other natural sugar-based polymers, chitosan molecules own versatile adhesion abilities to bind with various surfaces, owing to multiple functional moieties contained in the chain. To develop the promising biomaterials based on the chitosan chemistry, it is fundamentally important to figure out its adhesion mechanism under a certain condition, which leaves us numbers of open questions.

Discrimination of Protein Amino Acid or Its Protonated State at Single-Residue Resolution by Graphene Nanopores.

The function of a protein is determined by the composition of amino acids and is essential to proteomics. However, protein sequencing remains challenging due to the protein's irregular charge state and its high-order structure. Here, a proof of principle study on the capability of protein sequencing by graphene nanopores integrated with atomic force microscopy is performed using molecular dynamics simulations.

Study of DNA adsorption on mica surfaces using a surface force apparatus.

We report our studies on the adsorption properties of double-stranded DNA molecules on mica surfaces in a confined environment using a surface force apparatus. Specifically, we studied the influence of cation species and concentrations on DNA adsorption properties. Our results indicated that divalent cations (Mg(2+) and Co(2+)) preferred to form uniform and moderately dense DNA layers on a mica substrate.

Boronate complex formation with Dopa containing mussel adhesive protein retards ph-induced oxidation and enables adhesion to mica.

The biochemistry of mussel adhesion has inspired the design of surface primers, adhesives, coatings and gels for technological applications. These mussel-inspired systems often focus on incorporating the amino acid 3,4-dihydroxyphenyl-L-alanine (Dopa) or a catecholic analog into a polymer. Unfortunately, effective use of Dopa is compromised by its susceptibility to auto-oxidation at neutral pH.

Experimental observation of the ion-ion correlation effects on charge inversion and strong adhesion between mica surfaces in aqueous electrolyte solutions.

Direct force measurements between two mica surfaces in aqueous electrolyte solutions over broad ranges of LaCl3 concentrations and pH values were carried out with a surface forces apparatus. Charge inversion on mica surfaces is detected once the LaCl3 concentration reaches a critical value. With the continual increase of LaCl3 concentrations, the mica surface will be overscreened by the counterions.

Adaptive hydrophobic and hydrophilic interactions of mussel foot proteins with organic thin films.

The adhesion of mussel foot proteins (Mfps) to a variety of specially engineered mineral and metal oxide surfaces has previously been investigated extensively, but the relevance of these studies to adhesion in biological environments remains unknown. Most solid surfaces exposed to seawater or physiological fluids become fouled by organic conditioning films and biofilms within minutes. Understanding the binding mechanisms of Mfps to organic films with known chemical and physical properties therefore is of considerable theoretical and practical interest.

Adhesion of mussel foot protein Mefp-5 to mica: an underwater superglue.

Mussels have a remarkable ability to attach their holdfast, or byssus, opportunistically to a variety of substrata that are wet, saline, corroded, and/or fouled by biofilms. Mytilus edulis foot protein-5 (Mefp-5) is one of several proteins in the byssal adhesive plaque of the mussel M. edulis.