Oxidative stress-mediated N-terminal protein modifications and MS-based approaches for N-terminal proteomics

Metal Ion-Peptide-Intermediated Ligand Transfer for Serum Detection of the Omicron Variant of SARS-Cov-2 in Echinococcosis Patients

A method is developed to electrochemically induce target-specific covalent capturing of the spike protein of SARS-Cov-2, forming a covalent peptide-protein complex fit for working with such complicated clinical samples. Specifically, peptide-coordinated copper ions can be electrochemically controlled to induce cross-linkage between certain amino acids on the peptide probe and the target protein. Therefore, target specificity can be tuned electrochemically, realizing highly specific targeting of the omicron S protein or broader specificity toward all variants of the virus. Using this method, with electrochemically catalyzed generation of signal-enhancing molecules, the sensitivity and covalent detection allow their application in both serum and fecal samples. These results may point to their possible use in screening new variants of the virus in the near future.

A biocatalytic peptidobiosensing molecular bridge for detecting osteosarcoma marker protein

A biosensing scheme requiring only one-step sample incubation before signal collection, and using a compact "three-in-one" probe of target-binding, signal conversion, and amplification, may greatly simplify the design of biosensors. Therefore, sparing the multi-step addition of enzymes, protein, and nanomaterial, as well as the associated complexity and non-specific interactions. In this work, a peptide probe aimed at such compact features has been designed, based on protein-triggered, conformation-driven, and Cu (II) facilitated side-chain di-tyrosine cyclization. This design can use target-probe recognition to induce discriminated cross-linking and self-cleavage of the probe, resulting in retention or dissociation of a signal amplification motif from the search and consequently quantitative detection performance. The method has also been tested preliminarily in fractioned osteosarcoma clinical samples, showing an acceptable coherence between signal readout and clinical diagnosis. On the basis of these early findings, it is reasonable to assume that the proposed probe will be beneficial for the next development of tumor screening and prognosis sensors.

A Metal Ion-Controlled Molecular "Open Bridge" Detecting Oxidative Stress-Disrupted Apoptotic Signaling in Pediatric Neuroblastoma

Neuroblastoma is a metastatic tumor almost exclusively plaguing young children. To provide an early warning for timely medical interference that may prevent such tragedies from happening, we mimic the biomolecular pathology of this disease and have obtained an assay without using costly biomolecules such as antibodies and enzymes but can still sensitively detect trace level metal ions and metastatic marker proteins in the cerebrospinal fluid of neuroblastoma-bearing children in a one-step and reagentless fashion. Specifically, a surface-tethered "open bridge"-like molecular machine is designed. This probe, after interacting with cupric ions, can form an electrochemically active peroxidase-like artificial enzyme. Its activity first opens the probe, freeing the Bcl-2-targeting sequence of the probe to adopt the most favorable conformation, forming a noncovalent complex with Bcl-2. Then, the peroxidase-like activity of the probe induces the formation a robust fluorescence covalent linkage with the target protein. This fluorescence and electrochemical dual detection allows an analytical performance not inferior to the commercially available methods, pointing to possible clinical application in the early screening of pediatric metastatic conditions in the near future.

Enzyme-Initiated Assembly of an Extracellular-Like Two-Dimensional Nanonetwork as a Method to Detect Procancerous Activity

Extracellular matrix (ECM) enzymes such as lysyl oxidase (LOX) provide a new possibility to contain the invasive progress of cancer. Unlike conventional enzymes, the activity of ECM enzymes is not simply the conversion of the substrate to the product; the amount of enzymes such as matrix metalloproteinases in the ECM changes the structural integrity and morphology of the ECM. These are all important aspects that must be monitored in a spatiotemporally coupled fashion to fully understand their procancerous effect. To achieve this goal, a new molecular probe is developed, which, unlike antibodies or aptamers, can interact with the target enzyme in a more interactive way: the probe can withdraw the metal ion cofactor of the enzyme and modulate its catalytic ability. This can lead to self-propagated cross-linking of the probes to form a network not dissimilar to the collagen and elastin network of the ECM, formed through LOX activity. Thus, the biosensing process itself is a biomimetic of what may occur in vivo in the ECM, and three distinct types of signal readouts can be simultaneously recorded on the sensing surface to provide a fuller picture of ECM enzyme activity, not achievable with traditional designs. Using this method, a parallel between the detected signal and the progress of colorectal cancer can be observed. These results may point to prospective application of this method in evaluating ECM-related tumor invasiveness in the future.

Enabling Molecular Gapping and Bridging on a Biosensing Surface via Electrochemical Cross-Linking and Cleavage

Protein detection in complicated biological samples requires robust design and a rigorous rinsing process. Many recently developed artificial targeting probes, however, often do not possess antibody-like binding strength that enables them to endure harsh biosensing conditions, and the classic 2-to-1 sandwich binding pattern is unavailable for many targets, often necessitating a complicated indirect signal conversion mechanism. Here, an attempt is made to provide innovative "covalent" solutions to such problems by employing peptide reactivity to form a covalent and robust biosensing structure upon target binding. Both the cross-coupling and cleavage of peptide chains are employed to achieve the classic 2-to-1 binding when only one targeting probe is available. Specifically, a targeting probe against the protein and a signaling probe are coimmobilized onto the sensing interface. The ratio between the two probes and their surface density is modulated so that direct cross-linking between the two immobilized probes is suppressed by the average distance between two such probes. Upon protein binding, the protein molecule may bridge that gap by itself. The signaling probe can carry any motif of signal amplification. And here a Cu-ion-complexed motif, which can exhibit peroxidase-like activity upon electrochemical agitation, is employed multipurposely as the catalyst for cross-linking, cleavage, and signal amplification. Three nonhomologous target proteins can be sensitively quantified in serum-spiked samples and clinical sample detection of one of them is also successful; these results suggest the potential of the proposed method in future clinical applications.

Tamoxifen inhibits mitochondrial membrane damage caused by disulfiram

In this work, we studied the protective effects of tamoxifen (TAM) on disulfiram (Dis)-induced mitochondrial membrane insult. The results indicate that TAM circumvents the inner membrane leakiness manifested as Ca2+ release, mitochondrial swelling, and collapse of the transmembrane electric gradient. Furthermore, it was found that TAM prevents inactivation of the mitochondrial enzyme aconitase and detachment of cytochrome c from the inner membrane. Interestingly, TAM also inhibited Dis-promoted generation of hydrogen peroxide. Given that TAM is an antioxidant molecule, it is plausible that its protection may be due to the inhibition of Dis-induced oxidative stress.