Covalent Attachment Research Articles

Efficient in situ saccharification of microcrystalline cellulose over immobilized cellulase on magnetic biochar in ionic liquid media

Saccharification serves as the entry point for the biomass into biorefinery schemes and plays a vital role in lignocellulose transformation towards bio-fuels and platform molecules. Herein, an efficient in situ saccharification of lignocellulose under the mediation of ionic liquid of [DMIM]DMP is reported, using a series of magnetically-separable biochars as catalyst supports with immobilized endoglucanase Cel5A. The physicochemical properties of these magnetic biochars with immobilized endoglucanase (abbreviated as MBIE) were thoroughly characterized by FTIR, TG, SEM/EDX, XRD, XPS, N2 physisorption, UV–vis and VSM. The results revealed that the endoglucanase, which functions as the catalytically active species, was immobilized on the biochar via simultaneous physical adsorption and covalent attachment. The extremely high surface area of biochar endows a high loading of endoglucanase and easy diffusion of reactant within the catalyst’s framework. The zeta potential of the catalyst was − 7.06 mV, indicating its excellent stability. MBIE with immobilizing endoglucanase of 484.36 mg/g exhibited the superior performance under a biphasic system (IL/water v/v 5:1), affording a glucose yield of 932.5 mg/g. The activity of MBIE remained constant after 10 consecutive cycles via magnetic recycling. This work demonstrates an efficient in situ saccharification process catalyzed by the developed MBIE with high activity and excellent regeneration ability.

Synthetic Modifications of a Pb2+-Sensor Acridono-Crown Ether for Covalent Attachment and Their Effects on Selectivity.

Because of environmental impact, there is a great need for chemosensors, especially for toxic heavy metals such as lead. The conventional instrumental analytical techniques rarely provide an available real-time sensing platform, thus the development of highly selective and stable synthetic chemosensor molecules is of great importance. Acridono-18-crown-6 ethers have such properties, and much research has proven their outstanding applicability in various supramolecular devices. In this present work, we aimed to enable their covalent immobilization capability by synthesizing functionalized derivatives while preserving the favored molecular recognition ability. Several new macrocycle analogues were synthesized, while synthetization difficulties and design aspects were also dealt with. The selectivity of the macrocycle analogues was studied using UV-Vis spectroscopy and compared with that of the parent compounds. The ultimate crown ether derivative showed high Pb2+-selectivity, reversibility (decomplexation by extraction with water) and stability.

Copper-based metal-organic frameworks (BDC-Cu MOFs) as supporters for α-amylase: Stability, reusability, and antioxidant potential

Copper-based metal-organic frameworks (BDC-Cu MOFs) were synthesized via a casting approach using 1,4-benzene dicarboxylic (BDC) as organic ligand and their properties characterized. The obtained materials were then utilized to immobilize the α-amylase enzyme. The chemical composition and functional components of the synthesized support (BDC-Cu MOFs) were investigated with Fourier transform infrared spectroscopy (FTIR), the surface morphology was determined with scanning electron microscopy (SEM), and the elemental composition was established with energy dispersive X-ray (EDX) analyses. X-ray diffraction (XRD) was employed to analyze the crystallinity of the synthesized DBC-Cu MOFs. The zeta potentials of DBC-Cu MOFs and DBC-Cu MOFs@α-amylase were determined. The immobilized α-amylase demonstrated improved catalytic activity and reusability compared to the free form. Covalent attachment of the α-amylase to BDC-Cu provided an immobilization yield (IY%) of 81% and an activity yield (AY%) of 89%. The immobilized α-amylase showed high catalytic activity and 81% retention even after ten cycles. Storage at 4 °C for eight weeks resulted in a 78% activity retention rate for DBC-Cu MOFs@α-amylase and 49% retention for the free α-amylase. The optimum activity occurred at 60 °C for the immobilized form, whereas the free form showed optimal activity at 50 °C. The free and immobilized α-amylase demonstrated peak catalytic activities at pH 6.0. The maximum reaction velocities (Vmax) values were 0.61 U/mg of protein for free α-amylase and 0.37 U/mg of protein for BDC-Cu MOFs@α-amylase, while the Michaelis‒Menten affinity constants (Km) value was lower for the immobilized form (5.46 mM) than for the free form (11.67 mM). Treatments of maize flour and finger millet samples with free and immobilized α-amylase resulted in increased total phenolic contents. The enhanced antioxidant activities of the treated samples were demonstrated with decreased IC50 values in ABTS and DPPH assays. Overall, immobilization of α-amylase on BDC-Cu MOFs provided improved stability and catalytic activity and enhanced the antioxidant potentials of maize flour and finger millet.

Aerosol inhalation of inflammatory cells-targeted dendrimer-dexamethasone conjugate for efficient allergic asthma therapy.

Allergic asthma (AA) is a common breathing disorder clinically characterized by the high occurrence of acute and continuous inflammation. However, the current treatment options for AA are lacking in effectiveness and diversity. In this study, we determined that the cell membrane receptor of gamma-glutamyl transferase (GGT) was highly overexpressed on the inflammatory cells that infiltrate the pulmonary tissues in AA cases. Therefore, we developed a GGT-specific dendrimer-dexamethasone conjugate (GSHDDC) that could be administered via aerosol inhalation to treat AA in a rapid and sustained manner. The GSHDDC was fabricated by the covalent attachment of 6-hydroxyhexyl acrylate-modified dexamethasone to polyamidoamine dendrimers via a carbonic ester linkage and the amino Michael addition, followed by the surface modification of the dendrimers with the GGT substrate of glutathione. After aerosol inhalation by the AA mice, the small particle-sized GSHDDC could easily diffuse into pulmonary alveoli and touch with the inflammatory cells via the glutathione ligand/GGT receptor-mediated recognition. The overexpressed GGT on the surface of inflammatory cells then triggers the gamma-glutamyl transfer reactions of glutathione to generate positively charged primary amines, thereby inducing rapid cationization-mediated cellular endocytosis into the inflammatory cells. The dexamethasone was gradually released by the intracellular enzyme hydrolysis, enabling sustained anti-inflammatory effects (e.g., reducing eosinophil infiltration, decreasing the levels of inflammatory factors) in the ovalbumin-induced AA mice. This study demonstrates the effectiveness of an inhalational and active inflammatory cells-targeted dendrimer-dexamethasone conjugate for efficient AA therapy.

Friend or foe? Reciprocal regulation between E3 ubiquitin ligases and deubiquitinases.

Protein ubiquitination is a post-translational modification that entails the covalent attachment of the small protein ubiquitin (Ub), which acts as a signal to direct protein stability, localization, or interactions. The Ub code is written by a family of enzymes called E3 Ub ligases (∼600 members in humans), which can catalyze the transfer of either a single ubiquitin or the formation of a diverse array of polyubiquitin chains. This code can be edited or erased by a different set of enzymes termed deubiquitinases (DUBs; ∼100 members in humans). While enzymes from these distinct families have seemingly opposing activities, certain E3-DUB pairings can also synergize to regulate vital cellular processes like gene expression, autophagy, innate immunity, and cell proliferation. In this review, we highlight recent studies describing Ub ligase-DUB interactions and focus on their relationships.

Targeting of M2 macrophages with IL-13-functionalized liposomal prednisolone inhibits melanoma angiogenesis in vivo

The intricate cooperation between cancer cells and nontumor stromal cells within melanoma microenvironment (MME) enables tumor progression and metastasis. We previously demonstrated that the interplay between tumor-associated macrophages (TAMs) and melanoma cells can be disrupted by using long-circulating liposomes (LCLs) encapsulating prednisolone phosphate (PLP) (LCL-PLP) that inhibited tumor angiogenesis coordinated by TAMs. In this study, our goal was to improve LCL specificity for protumor macrophages (M2-like (i.e., TAMs) macrophages) and to induce a more precise accumulation at tumor site by loading PLP into IL-13-conjugated liposomes (IL-13-LCL-PLP), since IL-13 receptor is overexpressed in this type of macrophages. The IL-13-LCL-PLP liposomal formulation was obtained by covalent attachment of thiolated IL-13 to maleimide-functionalized LCL-PLP. C57BL/6 mice bearing B16.F10 s.c melanoma tumors were used to investigate the antitumor action of LCL-PLP and IL-13-LCL-PLP. Our results showed that IL-13-LCL-PLP formulation remained stable in biological fluids after 24h and it was preferentially taken up by M2 polarized macrophages. IL-13-LCL-PLP induced strong tumor growth inhibition compared to nonfunctionalized LCL-PLP at the same dose, by altering TAMs-mediated angiogenesis and oxidative stress, limiting resistance to apoptosis and invasive features in MME. These findings suggest IL-13-LCL-PLP might become a promising delivery platform for chemotherapeutic agents in melanoma.

Identification of novel tail-anchored membrane proteins integrated by the bacterial twin-arginine translocase.

The twin-arginine protein transport (Tat) system exports folded proteins across the cytoplasmic membranes of prokaryotes and the energy transducing-membranes of plant thylakoids and mitochondria. Proteins are targeted to the Tat machinery by N-terminal signal peptides with a conserved twin-arginine motif, and some substrates are exported as heterodimers where the signal peptide is present on one of the partner proteins. A subset of Tat substrates is found in the membrane. Tat-dependent membrane proteins usually have large globular domains and a single transmembrane helix present at the N- or C-terminus. Five Tat substrates that have C-terminal transmembrane helices have previously been characterized in the model bacterium Escherichia coli. Each of these is an iron-sulfur cluster-containing protein involved in electron transfer from hydrogen or formate. Here we have undertaken a bioinformatic search to identify further tail-anchored Tat substrates encoded in bacterial genomes. Our analysis has revealed additional tail-anchored iron-sulfur proteins associated in modules with either a b-type cytochrome or a quinol oxidase. We also identified further candidate tail-anchored Tat substrates, particularly among members of the actinobacterial phylum, that are not predicted to contain cofactors. Using reporter assays, we show experimentally that six of these have both N-terminal Tat signal peptides and C-terminal transmembrane helices. The newly identified proteins include a carboxypeptidase and a predicted protease, and four sortase substrates for which membrane integration is a prerequisite for covalent attachment to the cell wall.

Development and Immunological Evaluation of a Multiantigen Thermostable Nanovaccine Adjuvanted with T-Cell-Activating Scaffold for African Swine Fever.

African swine fever is an acute and highly contagious infectious disease with a mortality rate of up to 100%. The lack of commercial vaccines and drugs is a serious economic threat to the global pig industry. Cell-mediated immunity plays an essential role in protection against viral infection. We previously reported the rational design of a T-cell-activating thermostable scaffold (RPT) for antigen delivery and improved cellular immunity. We conjugated antigens P30, P54, P72, CD2 V, and CP312R to RPT, using a SpyCatcher/SpyTag covalent attachment strategy to construct nanovaccines (multiantigens-RPT). Multiantigens-RPT exhibited significantly higher thermal, storage, and freeze-thaw stability. The specific antibodies IgG and IgG2a of the multiantigen-RPT-immunized were higher than the antigens cocktail-immunized by approximately 10-100 times. ELISpot demonstrated that more IFN-γ-secreting cells were produced by the multiantigen-RPT-immunized than by the antigens cocktail-immunized. Delivery of the multiantigen nanovaccine by a T-cell-activating scaffold induced strong humoral and cellular immune responses in mice and pigs and is a potentially useful candidate vaccine for the African swine fever virus.

Cysteine-binding adjuvant enhances survival and promotes immune function in a murine model of acute myeloid leukemia

AbstractTherapeutic vaccination has long been a promising avenue for cancer immunotherapy but is often limited by tumor heterogeneity. The genetic and molecular diversity between patients often results in variation in the antigens present on cancer cell surfaces. As a result, recent research has focused on personalized cancer vaccines. Although promising, this strategy suffers from time-consuming production, high cost, inaccessibility, and targeting of a limited number of tumor antigens. Instead, we explore an antigen-agnostic polymeric in situ cancer vaccination platform for treating blood malignancies, in our model here with acute myeloid leukemia (AML). Rather than immunizing against specific antigens or targeting adjuvant to specific cell-surface markers, this platform leverages a characteristic metabolic and enzymatic dysregulation in cancer cells that produces an excess of free cysteine thiols on their surfaces. These thiols increase in abundance after treatment with cytotoxic agents such as cytarabine, the current standard of care in AML. The resulting free thiols can undergo efficient disulfide exchange with pyridyl disulfide (PDS) moieties on our construct and allow for in situ covalent attachment to cancer cell surfaces and debris. PDS-functionalized monomers are incorporated into a statistical copolymer with pendant mannose groups and TLR7 agonists to target covalently linked antigen and adjuvant to antigen-presenting cells in the liver and spleen after IV administration. There, the compound initiates an anticancer immune response, including T-cell activation and antibody generation, ultimately prolonging survival in cancer-bearing mice.

Three-step docking by WIPI2, ATG16L1, and ATG3 delivers LC3 to the phagophore.

The covalent attachment of ubiquitin-like LC3 proteins (microtubule-associated proteins 1A/1B light chain 3) prepares the autophagic membrane for cargo recruitment. We resolve key steps in LC3 lipidation by combining molecular dynamics simulations and experiments in vitro and in cellulo. We show how the E3-like ligaseautophagy-related 12 (ATG12)-ATG5-ATG16L1 in complex with the E2-like conjugase ATG3 docks LC3 onto the membrane in three steps by (i) the phosphatidylinositol 3-phosphate effector protein WD repeat domain phosphoinositide-interacting protein 2 (WIPI2), (ii) helix α2 of ATG16L1, and (iii) a membrane-interacting surface of ATG3. Phosphatidylethanolamine (PE) lipids concentrate in a region around the thioester bond between ATG3 and LC3, highlighting residues with a possible role in the catalytic transfer of LC3 to PE, including two conserved histidines. In a near-complete pathway from the initial membrane recruitment to the LC3 lipidation reaction, the three-step targeting of the ATG12-ATG5-ATG16L1 machinery establishes a high level of regulatory control.

Plasma‐Activated Coated Glass: A Novel Platform for Optimal Optical Performance and Cell Culture Substrate Customization

Borosilicate glass surpasses polystyrene in optical quality; however, it is less frequently used for cell culture due to poor protein and cell adhesion. To overcome this impasse, the surface of glass coverslips requires functionalization to enable facile covalent attachment of proteins to promote cell attachment and differentiation. Herein, a novel approach is presented to covalently attach proteins to glass by depositing a thin layer of radical‐rich carbon film using a plasma polymerization process. The surface chemistry of these plasma‐activated coatings can be controlled by varying the gas composition used during the deposition. Mass spectrometry reveals different protein profiles attached to functionalized glass coverslips when they are exposed to cell culture media. Mouse embryonic stem cell adhesion and subsequent differentiation into neural lineage on plasma‐treated coverslips are significantly enhanced compared to bare coverslips. Importantly, the coatings are in the nanometer range, preserve the optical properties of the glass coverslips for imaging, and remain stable for at least 4 weeks in simulated body fluid. These results demonstrate the utility of covalently attaching proteins to glass for enhanced cell attachment and stem cell differentiation and provide a promising technique to achieve better outcomes in cell culture in a range of biomedical applications.

Covalent Attachment of Sulfur-doped Graphene Quantum Dots to Glucose Oxidase via Diimide-activated Amidation

The conjugation of biomolecules to quantum dots has recently gained attention in the field of bionanotechnology. Graphene quantum dots (GQDs) have been employed in various sensing applications due to their tunable fluorescence, controllable size, low cytotoxicity, and high biocompatibility. In this work, sulfur-doped graphene quantum dots (S-GQDs) were conjugated to glucose oxidase (GOx) for the potential detection of glucose. Fluorescent S-GQDs were synthesized via one-step pyrolysis of citric acid and thioglycolic acid at 200 °C. S-GQDs were conjugated to GOx using the carbodiimide/succinimide (EDC/NHS) coupling reaction, followed by purification via centrifugal ultrafiltration. Fluorescence spectroscopy, UV-Vis absorption spectroscopy, and transmission electron microscopy were employed to characterize the S-GQDs and S-GQD-GOx conjugates. The S-GQDs obtained had an average diameter of 49.8 ± 7.4 nm (n = 12) and emitted strong blue fluorescence (λem = 460 nm) when excited with 365-nm UV light. Trinder’s assay was used to assess the catalytic activity of free GOx and the S-GQD-GOx conjugates. The S-GQD-GOx conjugates consistently showed significantly greater catalytic activity compared to free GOx. The results obtained open avenues for the fabrication of a sensitive fluorescent GQD-based glucose probe in the future.

The logic of protein post-translational modifications (PTMs): Chemistry, mechanisms and evolution of protein regulation through covalent attachments.

Protein post-translational modifications (PTMs) play a crucial role in all cellular functions by regulating protein activity, interactions and half-life. Despite the enormous diversity of modifications, various PTM systems show parallels in their chemical and catalytic underpinnings. Here, focussing on modifications that involve the addition of new elements to amino-acid sidechains, I describe historical milestones and fundamental concepts that support the current understanding of PTMs. The historical survey covers selected key research programmes, including the study of protein phosphorylation as a regulatory switch, protein ubiquitylation as a degradation signal and histone modifications as a functional code. The contribution of crucial techniques for studying PTMs is also discussed. The central part of the essay explores shared chemical principles and catalytic strategies observed across diverse PTM systems, together with mechanisms of substrate selection, the reversibility of PTMs by erasers and the recognition of PTMs by reader domains. Similarities in the basic chemical mechanism are highlighted and their implications are discussed. The final part is dedicated to the evolutionary trajectories of PTM systems, beginning with their possible emergence in the context of rivalry in the prokaryotic world. Together, the essay provides a unified perspective on the diverse world of major protein modifications.

Carbon-nanotube field-effect transistors for resolving single-molecule aptamer-ligand binding kinetics.

Small molecules such as neurotransmitters are critical for biochemical functions in living systems. While conventional ultraviolet-visible spectroscopy and mass spectrometry lack portability and are unsuitable for time-resolved measurements in situ, techniques such as amperometry and traditional field-effect detection require a large ensemble of molecules to reach detectable signal levels. Here we demonstrate the potential of carbon-nanotube-based single-molecule field-effect transistors (smFETs), which can detect the charge on a single molecule, as a new platform for recognizing and assaying small molecules. smFETs are formed by the covalent attachment of a probe molecule, in our case a DNA aptamer, to a carbon nanotube. Conformation changes on binding are manifest as discrete changes in the nanotube electrical conductance. By monitoring the kinetics of conformational changes in a binding aptamer, we show that smFETs can detect and quantify serotonin at the single-molecule level, providing unique insights into the dynamics of the aptamer-ligand system. In particular, we show the involvement of G-quadruplex formation and the disruption of the native hairpin structure in the conformational changes of the serotonin-aptamer complex. The smFET is a label-free approach to analysing molecular interactions at the single-molecule level with high temporal resolution, providing additional insights into complex biological processes.

Enzymatic Processing of DNA-Protein Crosslinks.

DNA-protein crosslinks (DPCs) represent a unique and complex form of DNA damage formed by covalent attachment of proteins to DNA. DPCs are formed through a variety of mechanisms and can significantly impede essential cellular processes such as transcription and replication. For this reason, anti-cancer drugs that form DPCs have proven effective in cancer therapy. While cells rely on numerous different processes to remove DPCs, the molecular mechanisms responsible for orchestrating these processes remain obscure. Having this insight could potentially be harnessed therapeutically to improve clinical outcomes in the battle against cancer. In this review, we describe the ways cells enzymatically process DPCs. These processing events include direct reversal of the DPC via hydrolysis, nuclease digestion of the DNA backbone to delete the DPC and surrounding DNA, proteolytic processing of the crosslinked protein, as well as covalent modification of the DNA-crosslinked proteins with ubiquitin, SUMO, and Poly(ADP) Ribose (PAR).

Simple methods for measuring milk exosomes using fluorescent compound GIF-2250/2276

Exosomes are small extracellular vesicles (EVs) found in culture supernatants, blood, and breast milk. The size of these nanocomplexes limits the methods of EV analyses. In this study, nitrobenzoxadiazole (NBD), a fluorophore, conjugated endosome-lysosome imager, GIF-2250 and its derivative, GIF-2276, were evaluated for exosome analyses. A correlation was established between GIF-2250 intensity and protein maker levels in bovine milk exosomes. We found that high-temperature sterilization milk may not contain intact exosomes. For precise analysis, we synthesized GIF-2276, which allows for the covalent attachment of NBD to the Lys residue of exosome proteins, and labeled milk exosomes were separated using a gel filtration system. GIF-2276 showed chromatographic peaks of milk exosomes containing >3 ng protein. The area (quantity) and retention time (size) of the exosome peaks were correlated to biological activity (NO synthesis suppression in RAW264.7 murine macrophages). Heat denaturation of purified milk-derived exosomes disrupted these indicators. Proteome analyses revealed GIF-2276-labeled immunomodulators, such as butyrophilin subfamily 1 member A1 and polymeric immunoglobulin receptor. The immunogenicity and quantity of these factors decreased by heat denaturation. When milk exosomes were purified from market-sourced milk we found that raw and low-temperature sterilization milk samples, contained exosomes (none in high-temperature sterilization milk). These results were also supported by transmission electron microscopy analyses. We also found that GIF-2276 could monitor exosome transportation into HEK293 cells. These results suggested that GIF-2250/2276 may be helpful to evaluate milk exosomes.

RFX transcription factor in the human-associated yeast Candida albicans regulates adhesion to oral epithelium.

Adhesion to mucosal surfaces is a critical step in many bacterial and fungal infections. Here, using a mouse model of oral infection by the human fungal pathobiont Candida albicans, we report the identification of a novel regulator of C. albicans adhesion to the oral mucosa. The regulator is a member of the regulatory factor X (RFX) family of transcription factors, which control cellular processes ranging from genome integrity in model yeasts to tissue differentiation in vertebrates. Mice infected with the C. albicans rfx1 deletion mutant displayed increased fungal burden in tongues compared to animals infected with the reference strain. High-resolution imaging revealed RFX1 transcripts being expressed by C. albicans cells during infection. Concomitant with the increase in fungal burden, the rfx1 mutant elicited an enhanced innate immune response. Transcriptome analyses uncovered HWP1, a gene encoding an adhesion protein that mediates covalent attachment to buccal cells, as a major RFX1-regulated locus. Consistent with this result, we establish that C. albicans adhesion to oral cells is modulated by RFX1 in an HWP1-dependent manner. Our findings expand the repertoire of biological processes controlled by the RFX family and illustrate a mechanism whereby C. albicans can adjust adhesion to the oral epithelium.

The Deubiquitylase Otub1 Regulates the Chemotactic Response of Splenic B Cells by Modulating the Stability of the γ-Subunit Gng2.

The ubiquitin proteasome system performs the covalent attachment of lysine 48-linked polyubiquitin chains to substrate proteins, thereby targeting them for degradation, while deubiquitylating enzymes (DUBs) reverse this process. This posttranslational modification regulates key features both of innate and adaptative immunity, including antigen presentation, protein homeostasis and signal transduction. Here we show that loss of one of the most highly expressed DUBs, Otub1, results in changes in murine splenic B cell subsets, leading to a significant increase in marginal zone and transitional B cells and a concomitant decrease in follicular B cells. We demonstrate that Otub1 interacts with the γ-subunit of the heterotrimeric G protein, Gng2, and modulates its ubiquitylation status, thereby controlling Gng2 stability. Proximal mapping of Gng2 revealed an enrichment in partners associated with chemokine signaling, actin cytoskeleton and cell migration. In line with these findings, we show that Otub1-deficient B cells exhibit greater Ca2+ mobilization, F-actin polymerization and chemotactic responsiveness to Cxcl12, Cxcl13 and S1P invitro, which manifests invivo as altered localization of B cells within the spleen. Together, our data establishes Otub1 as a novel regulator of G-protein coupled receptor signaling in B cells, regulating their differentiation and positioning in the spleen.

Microscale manipulation of bond exchange reactions in photocurable vitrimers with a covalently attachable photoacid generator.

Vitrimers are polymer networks with covalent bonds that undergo reversible exchange reactions and rearrange their topology in response to an external stimulus. The temperature-dependent change in viscoelastic properties is conveniently adjusted by selected catalysts. In these thermo-activated systems, the lack in spatial control can be overcome by using photolatent catalysts. Herein, we advance this concept to locally manipulate bond exchange reactions on a single digit microscale level. For this, we synthetize a linkable non-ionic photoacid generator, which is covalently attached to a thiol-click photopolymer. UV induced deprotection of the photoacid yields a strong immobilized sulfonic acid species, which is able to efficiently catalyze transesterification reactions. Covalent attachment of the formed acid prevents migration/leaching processes and enables a precise tuning of material properties. As proof of concept, positive toned microstructures with a resolution of 5 μm are inscribed in thin films using direct two-photon absorption laser writing and subsequent depolymerization. In addition, the possibility to locally reprogram bulk material properties is demonstrated by performing a post-modification reaction with ethylene glycol and carboxylic acids. The Young's modulus is varied between 3.3 MPa and 11.9 MPa giving rise to the versatility of the newly introduced catalysts for creating light processable and transformable materials.

Water-soluble photocatalysts based on porphyrin-carbon dot conjugates produce H2 under visible light irradiation.

Herein, we report visible-light-induced hydrogen generation from aqueous protons utilizing a novel hybrid photocatalytic nanomaterial comprising porphyrin-carbon dot conjugates. Amide coupling between metallated tetra-carboxyphenyl porphyrins (MTCPPs) and nitrogen doped carbon dots (NCDots) was performed to afford M-TCPP-NCDots hybrids, which were applied in hydrogen evolution photocatalysis under visible irradiation. H2 was obtained in the presence of appropriate sacrificial electron donors and with no additional metallic co-catalysts. It is noteworthy that the covalent attachment as well as the zinc-metallation of the porphyrin moiety were proved vital for the efficiency of the present system. The present study constitutes an innovative approach for artificial photosynthesis avoiding the use of costly materials such as noble metals.