Chemoselective and Site-Selective Lysine-Directed Lysine Modification Enables Single-Site Labeling of Native Proteins

The necessity for precision labeling of proteins emerged during the efforts to understand and regulate their structure and function. It demands selective attachment of tags such as affinity probes, fluorophores, and potent cytotoxins. Here, we report a method that enables single-site labeling of a high-frequency Lys residue in the native proteins. At first, the enabling reagent forms stabilized imines with multiple solvent-accessible Lys residues chemoselectively. These linchpins create the opportunity to regulate the position of a second Lys-selective electrophile connected by a spacer. Consequently, it enables the irreversible single-site labeling of a Lys residue independent of its place in the reactivity order. The user-friendly protocol involves a series of steps to deconvolute and address chemoselectivity, site-selectivity, and modularity. Also, it delivers ordered immobilization and analytically pure probe-tagged proteins. Besides, the methodology provides access to antibody-drug conjugate (ADC), which exhibits highly selective anti-proliferative activity towards HER-2 expressing SKBR-3 breast cancer cells.     

NIR triggered NaYF4:Yb3+,Tm3+@NaYF4/CsPb(Br1-x/Ix)3 composite for up-converted white-light emission and dual-model anti-counterfeiting applications

Assembling nanomaterials from two classes with exceptional control at the nanoscale can lead to new nanohybrids with novel properties. Here, we report the tunable up-conversion luminescence properties of CsPb(Br_1-x/I_x)₃ perovskite nanocrystals (PeNCs) sensitized by NaYF₄:Yb,Tm@NaYF₄ up-conversion nanoparticles (UCNPs) at 980 nm excitation. The up-conversion luminescence of NaYF₄:Yb³⁺,Tm³⁺@NaYF₄/CsPb(Br_1-x/I_x)₃ composite demonstrates that the radiative photon reabsorption process is accountable for the UC energy transfer from excited levels of Tm³⁺-based UCNPs to PeNCs. The long-lived Tm³⁺ states feed PeNCs carriers with intrinsic lifetimes extending from nanoseconds to microseconds. By varying the UCNPs/PeNCs concentration ratio, the NaYF₄:Yb³⁺,Tm³⁺@NaYF₄/CsPb(Br_0.55I_0.45)₃ composite generates UC white light emission. The near-infrared excited white light-emitting devices are more compatible with human tissues than blue light-excited ones. Therefore, the prototype of UC white light-emitting diode is developed by coupling the UCNPs/PeNCs composite coated glass plate onto a commercial 940 nm-light-emitting diode chip. To overcome the counterfeiting risk that arises in the case of a single fluorescence mode, we developed a simple dual-model strategy based on manipulation of UC and down-conversion luminescence in anti-counterfeiting under 980 nm and 365 nm excitation, which makes it difficult to encrypt the information. In addition, the UCNPs/PeNCs composite exhibited better photostability under near-infrared illumination, retaining 85% of initial photoluminescence intensity, solving the problem of photo-instability.     

Mechanical Properties of Regenerated Cellulose Fibres for Composites

Summary: A broad variety of regenerated cellulose fibres was subjected to single fibre tensile tests in order to determine the modulus of elasticity, tensile strength, and failure strain. The results were compared to glass fibres and flax fibres, which are considered the most important technical and natural fibres, respectively. With regard to their modulus of elasticity and tensile strength, regenerated cellulose fibres showed clearly lower values than glass fibres, even when their low density was taken into account. The average modulus of elasticity and tensile strength of regenerated cellulose fibres was also lower than the values measured for flax fibres, but when variability was considered, both fibres performed similarly. In terms of interfacial shear strength with polypropylene, lyocell fibres performed significantly less well than sized glass fibre and ramie fibre. The most important difference between regenerated cellulose fibres and both glass and flax fibres is their high failure strain and thus high work to fracture. The high work to fracture of regenerated cellulose fibres makes them particularly useful for composite applications where high fracture toughness is required.