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• Three novel linear PTO-based COPs was fabricated via Suzuki coupling reaction. • The P(PTODB)-2 shows a high initial specific capacity of 210 mA h g-1 at 0.1 A g-1. • Superior rate properties (150 mA h g-1 at 5 A g-1) could be achieved. • The ex-situ FT-IR and XPS tests have proved lithium storage mechanism with C=O groups. Conjugated organic polymers (COPs) have been emerged as a class of cathode materials for lithium-ion batteries (LIBs) because of the rigid structural units and tunable properties. Nonetheless, their applications are still limited due to the poor conductivity and low cycling life. Herein, we design a series of pyrene-4,5,9,10-tetraone-based COPs (P(PTODB)-1, P(PTODB)-2, P(PTODB)-3), containing different number of benzene rings as linking units. Consequently, prolonging the linker lengths could effectively improve structural stability and extend π-conjugation, leading to the enhanced charge-storage capability. When tested as cathode materials for LIBs, the P(PTODB)-2 electrode delivers a better electrochemical performance with high capacity of 203 mA h g-1 after 100 cycles at 0.1 A g-1 (coulombic efficiency almost 100%) and excellent rate performance (150 mA h g-1 at 5 A g-1). In addition, the Li+ storage mechanism was carried out by ex situ Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis. Eventually, our study brings forward the appropriately extended linker lengths to fabricate COP cathodes with high electrochemical properties. [Display omitted] [ABSTRACT FROM AUTHOR]

In addition to replicative histones, eukaryotic genomes encode a repertoire of non-replicative variant histones, providing additional layers of structural and epigenetic regulation. Here, we systematically replace individual replicative human histones with non-replicative human variant histones using a histone replacement system in yeast. We show that variants H2A.J, TsH2B, and H3.5 complement their respective replicative counterparts. However, macroH2A1 fails to complement, and its overexpression is toxic in yeast, negatively interacting with yeast's native histones and kinetochore genes. To isolate yeast with macroH2A1 chromatin, we uncouple the effects of its macro and histone fold domains, revealing that both domains suffice to override native nucleosome positioning. Furthermore, both uncoupled constructs of macroH2A1 exhibit lower nucleosome occupancy, decreased short-range chromatin interactions (<20 kb), disrupted centromeric clustering, and increased chromosome instability. Our observations demonstrate that lack of a canonical histone H2A dramatically alters chromatin organization in yeast, leading to genome instability and substantial fitness defects. [Display omitted] • Expanded toolset for swapping histones in S. cerevisiae • Complementation tests between human replicative histones and their variants • Amino acid swapping experiments between replicative human H2A and macroH2A1.2 • Human macroH2A1.2 alters the structure of yeast chromatin fiber locally and at long range Haase et al. used a genetic swapping assay to replace replicative human histones with non-replicative variants in yeast. H2A.J, TsH2B, and H3.5 complemented their replicative counterparts, while macroH2A1.2 proved toxic, disrupting chromatin organization, increasing nucleosome repeat length, and—when associated with chromosome instability—leading to fitness defects in yeast. [ABSTRACT FROM AUTHOR]

Drug-drug conjugate nanoparticles (DDC NPs) is a potential method for overcoming poor solubility and nonspecific action in cancer therapy, which is based on its high drug loading efficiency and passive tumor-target properties. Our laboratory has prepared DOX-SS-DOX NPs based on disulfide-linked doxorubicin (DOX) drug-drug conjugate, which showed well physical stability and similar anti-tumor efficacy as liposomes. However, how structures of DDCs influence the self-assembling and anti-tumor efficacy is still seldom clarified and needs further investigation. Here, we discussed the role of linker types, length and linkage site in the NPs self-assembling and anti-tumor efficacy. A series of DOX prodrugs were prepared and all the prodrugs could self-assemble into NPs except DOX-SS-DOX (2), indicating the linker length played an important role during self-assembling process. The linkage sites and types of linker exhibited great influence on in vitro cytotoxicity and in vivo anti-tumor efficacy, particularly, modification on C-14 hydroxyl was more efficient for DOX release than on amino group. Besides, disulfide-bond was not cleaved and DOX-SH release did not occur in the metabolism process. The function of disulfide-bond was to enhance the release of DOX in the hydrolysis process. These findings is meaningful for effective prodrug NPs design for therapeutics. [ABSTRACT FROM AUTHOR]

Peptide linkers of three different lengths were constructed to join the variable regions of the heavy chain (VH) and the light chain (VL) in a single-chain variable fragment antibody (scFv) specific for wogonin glucuronide (Wgn) that has the structure VH-(GGGGS) n –VL ( n = 3, 5, or 7). The scFv antibodies, which were expressed in Escherichia coli , were derived from an anti-Wgn monoclonal antibody (315A). An indirect competitive enzyme-linked immunosorbent assay (icELISA) was used to evaluate their reactivity and sensitivity, which is also used for quantitative analysis of Wgn. Our results, showed that the reactivity and specificity of the three different scFvs were, in fact, similar. Subsequently, the scFv having a VH-(GGGGS) 3 –VL linker which was slightly better that other two scFvs against Wgn, was applied to indirect competitive ELISA (icELISA) to analyze Scutellariae Radix (S. Radix). The utility of the icELISA was demonstrated for quality control and analysis of S. Radix in this report. [ABSTRACT FROM AUTHOR]

Highlights: [•] We investigated bispyridinium compounds in binding experiments with nAChRs. [•] We compared [3H]epibatidine affinity profiles to the inhibition of human AChE. [•] nAChR affinity and AChE inhibition depended on linker length. [•] Divalent cations enhanced [3H]epibatidine binding. [ABSTRACT FROM AUTHOR]

Abstract: α1-adrenoceptor (α1-AR) subtype-selective ligands lacking off-target affinity for the 5-HT1A receptor (5-HT1A-R) will provide therapeutic benefits in the treatment of urogenital conditions such as benign prostatic hyperplasia. In this study we determined the affinity of 4-aminoquinoline and eleven homobivalent 4-aminoquinoline ligands (diquinolines) with alkane linkers of 2–12 atoms (C2–C12) for α1A, α1B and α1D -ARs and the 5-HT1A-R. These ligands are α1A-AR antagonists with nanomolar affinity for α1A and α1B -ARs. They display linker-length dependent selectivity for α1A/B -ARs over α1D-AR and the 5-HT1A-R. The C2 diquinoline has the highest affinity for α1A-AR (pK i 7.60±0.26) and greater than 30-fold and 600-fold selectivity for α1A-AR over α1D-AR and 5-HT1A-R respectively. A decrease in affinity for α1-ARs is observed as the linker length increases, reaching a nadir at 5 (α1A/1B-ARs) or 6 (α1D-AR) atoms; after which affinity increases as the linker is lengthened, peaking at 9 (α1A/1B/1D-ARs) or 8 (5-HT1A-R) atoms. Docking studies suggest that 4-aminoquinoline and C2 bind within the orthosteric binding site, while for C9 one end is situated within the orthosteric binding pocket, while the other 4-aminoquinoline moiety interacts with the extracellular surface. The limited α1D-AR and 5-HT1A-R affinity of these compounds makes them promising leads for future drug development of α1A-AR selective ligands without α1D-AR and the 5-HT1A-R off-target activity. [Copyright &y& Elsevier]

Abstract: Peptides involving the RGD motive (arginine–glycine–aspartic acid) recognize members of the integrin receptor family. Since the receptors are located mainly on the surface of endothelial cells, structural modifications including multimers of c(RGDfE) were recently found to improve the binding avidity for αvβ3 integrin significantly. The multivalent RGD peptides exhibited rather loose linkages partly including oligo(ethylene glycol) spacers (EG n ) with different chain lengths. Therefore, the dependence of multivalent RGD systems with and without EG n linkers were investigated on their binding properties to cultured αvβ3 integrin-expressing U87MG cells. Methods: We synthesized a series of di-, tri- and tetravalent rigid scaffolds (terephthalic acid, trimesic acid and adamantane-1,3,5,7-tetracarboxylic acid) conjugated to c(RGDyK) ligands, which were linked contiguously or separated by the oligo(ethylene glycol) spacers. The inhibition constants of these c(RGDyK) derivatives were determined by competition assays with 125I-labeled echistatin. Results: While c(RGDyK) function is a relative weak competitor against [125I]echistatin (K i, 329±18 nM) for αvβ3 integrin-expressing U87MG cells, RGD dimers improved the competition potency considerably (K i, 64±23 nM). This effect was even more pronounced with the RGD trimers (K i, 40±7 nM) and tetramers (K i, 26±9 nM). The introduction of EG n spacers and the increase of linker lengths proved to be detrimental since more competitors were needed to compete with [125I]echistatin. The EG 6 group, for example, reduced the inhibition constants by 29% (dimer), 57% (trimer) and 97% (tetramer). Conclusion: The binding experiments performed with the three forms of multivalent RGD ligands indicate the weakening of competitive potency against [125I]echistatin with the introduction of EG n spacers. This effect may be related to the decrease of the effective RGD molarity, which becomes most prominent within the tetravalent series. [Copyright &y& Elsevier]

Adopting carbon nanotube (CNT) transistors as biosensors has been developed as a promising method for cancer biomarker detection, which has shown superior sensitivity and selectivity. However, the detection of circulating tumor DNA (ctDNA) by the CNT transistor based biosensors is still a challenge and no work has been reported. Here, direct label-free DNA detection of AKT2 gene related to triple-negative breast cancer by all-CNT thin-film transistor (TFT) biosensors incorporated with tetrahedral DNA nanostructures (TDNs) is proposed and achieved for the first time. The adoption of TDNs enables improved biosensor response for at least 35% and even as high as 98% as compared with single-stranded DNA (ssDNA) probes owing to the enhanced DNA hybridization efficiency. Influence of the TDNs' linker length on the biosensor performance is important and has been investigated. Concentration-dependent DNA detection is achieved by the all-CNT TFT biosensors with a broad linear detection range of six orders of magnitude and a theoretical limit of detection (LOD) of 2 fM. In addition, the all-CNT TFT biosensors exhibit favorable selectivity and repeatability. The platform of all-CNT TFT biosensors incorporated with TDNs has great potential for multiplexed detection of various cancer biomarkers, providing a simple yet high performance universal strategy for low-cost clinical applications. • A tetrahedral DNA nanostructure (TDN) based all-carbon nanotube thin-film transistor biosensor was developed. • The adoption of TDNs enables improved biosensor response for as high as 98% as compared with single-stranded DNA probes. • DNA detection of AKT2 gene was achieved with a linear detection range from 1 pM to 1 μM and a detection limit of 2 fM. • The effect of TDNs' linker length on the biosensor performance was investigated. [ABSTRACT FROM AUTHOR]

Abstract: Development of tumor targeting pharmaceuticals on a modular platform is an attractive paradigm. Design choices for bispecific (anti-tumor and anti-chelate) pretargeting molecules are increased by the use of scFvs. Because a scFv is monovalent and small in size, its functional affinity and in vivo residence time can be improved through multimerization. ScFv multimers can be covalent or non-covalent. In vivo studies indicate that covalent scFv multimers are preferable. Attachment of scFv modules to scaffolds offers a wide range of possibilities for size and valency. A free thiol introduced at the C terminal end of a scFv (scFv-SH) allows for site-specific covalent attachment to a PEG scaffold without interfering with its antigen (Ag) binding. Although in theory, multimerization of 3 or 4 scFvs can be achieved by direct conjugation, as scFv-SH, to a tri or tetrafunctionalized PEG, it is not a practical option since homogeneous tri and tetrafunctionalized PEG are not readily available. However, the generation of (scFv)3–4-PEG molecules through attachment of combinations of di-scFv-SH (tandemly expressed scFvs) and scFv-SH or 2 di-scFv-SH to a bifunctional PEG is a sound approach that also allows for better control of the scFv-PEG conjugate molecular composition. Optimization of the molecular format of the di-scFv-SH module for production as soluble proteins in E. coli, Ag binding and conjugation is reported in this study. ScFvs in the VH-VL format were used for the di-scFv constructs since Fv domain inversion to VL-VH, while not yielding more protein, also abolished Ag binding. The effects on production yield, Ag binding and conjugation potential of the scFv joining linker length and the presence and location of an engineered cysteine were assessed in vitro. Our data indicate that for di-scFv-SH, an increase of the scFv joining linker length results in higher production and better Ag binding; a 20 aa long linker (G4S)4 was the longest linker tested. For the engineered cysteine, three locations were tested; within the scFv joining linker, at the C terminus upstream of the E Tag and as the carboxy terminal aa. The accessibility of the free SH assessed by conjugation of di-scFv-SH to HRP-Mal demonstrated that di-scFv-HRP conjugates are formed with comparable efficiencies when the cysteine is located at the scFv carboxy end. This empirical work provides a framework for the development of bispecific scFv multimers via site-specific attachment of scFv-SH and di-scFv-SH modules to a scaffold. [Copyright &y& Elsevier]

Our previous studies revealed that the nonapeptide fragment of HLA-DR molecule, located in the β chain 164–172 with the VPRSGEVYT sequence, suppresses the immune responses. The sequence is located on the exposed molecule loop, therefore it may be involved in the interactions with other proteins. We suggested that the loop may serve as a functional epitope on the HLA class II surface for intermolecular binding, and that possible mechanism of biological action of the synthesized peptides is associated with interfering of adhesion of HLA class II molecules to their coreceptors. It has been postulated that oligomerization of the coreceptors is required for stable binding to class II HLA. Based on the crystal dimeric structure of HLA-DR molecules, we designed, and synthesized molecules able to induce the putative coreceptors dimerization. The synthesized series of compounds consisted of two VPRSGEVYT sequences linked through their C-termini by spacers of different length: (VPRSGEVYTGn)2K-NH2 (n=4–6). The results demonstrate that the dimerization of the nonapeptide fragment of HLA-DR results in enhanced immunosuppressory properties. [Copyright &y& Elsevier]

• A streamlined, convenient, and modular two-enzyme complex was constructed. • The enzyme complex with the semirigid linker FRRRF showed the highest initial reaction rate. • Precise linker length and flexibility enable the efficient catalysis of the enzyme complex. Synthetic enzyme complexes have been successfully used to accelerate the reaction rate of cascade enzyme biocatalysis. Protein scaffold-mediated enzyme complexes are often constructed by assembling cascade enzymes on the artificial protein scaffoldin to form sophisticated biomimetic architectures and enhance the catalytic efficiency of biocatalytic processes. However, the effects of the linker in scaffoldin on the performance of the enzyme complexes have not been clarified. In this study, a scaffoldin-mediated two-enzyme complex containing triosephosphate isomerase (TIM) and fructose-1,6-bisphosphate aldolase/phosphatase (FBPA) was constructed, and the initial production rate of fructose 6-phosphate (F6P) was determined with different types of fine-tuning linkers. Enzyme complexes with linker length of 25 amino acids in scaffoldin exhibited the highest initial F6P production rate compared with linker length of 0, 10, or 57 amino acids in scaffoldin. This result indicated that an appropriate interdomain spacing between functional domains was required by multienzyme complexes to facilitate effective cascade catalysis. Then, the most popular flexible linker GGGGS (unit F) and rigid linker EAAAK (unit R) were introduced into this 25 amino acid linker to investigate the effect of linker flexibility on the initial reaction rate of the TIM–FBPA enzyme complex. The synthetic enzyme complex with the semirigid linker FRRRF in scaffoldin showed the highest initial F6P production rate of 10.16 μM/min, which indicates that the linker's amino acid composition in scaffoldin may lead to significant changes in the spatial architecture of the TIM–FBPA complex and consequently affect the initial reaction rate. Precise linker length and flexibility allow an appropriate interdomain conformation to enable efficient cascade reactions. Collectively, our results showed that fine-tuning the initial reaction rate of enzyme complexes is an integrated systematic engineering, including adjusting the multienzyme architecture, linker length, and linker flexibility, which provides rational guidance for designing effective multienzyme complexes in the future. [ABSTRACT FROM AUTHOR]