Research On The Fabrication Of Porphyrin-Based Molecular Machines And Their Applications In Bioanalytical Detection

A molecular machine is composed of two or more molecular units.After a suitable external energy stimulus,relative displacement occurs between the molecular units,thereby converting energy into mechanical motion.Extending the concept of machines to the molecular level is not only for basic research,but also for the development of nanoscience and the subsequent development of nanotechnology.First,a sandwich metal porphyrin complex La（TPy P）₂ based on 5,10,15,20-tetra（4-pyridyl）porphyrin was synthesized.Through a series of optical analysis methods,it has confirmed its excellent optical performance.Compared with its porphyrin monomer that emits a weak ECL signal with the participation of tripropylamine,La（TPy P）₂ can have two strong ECL emission peaks at 730 nm and 784 nm,indicating that the participation of metal ions enhances the porphyrin The electrochemical activity.With the addition of protic acid,the rotation of the porphyrin ligand may be accelerated,thereby enhancing the electrochemiluminescence of the La（TPy P）₂/acetonitrile system in the acetonitrile solution.On the contrary,after the addition ofβ-cyclodextrin and other adsorbents,the rotation of the porphyrin ligand may be restricted,which inhibits the electrochemiluminescence of the La（TPy P）₂/acetonitrile system in the acetonitrile solution.This sandwich-type metalloporphyrin enhances or inhibits ECL signals by regulating rotation,which provides an important reference for the application of biomolecular machines in the field of ECL bioassays.The hemoglobin molecule is an extremely efficient molecular machine that regulates its behavior through movement and small structural changes.The combination of oxygen and hemoglobin at the four sites is not synchronized.The first combination of oxygen and hemoglobin causes small changes in the corresponding protein chains,and these changes make it easier for them to bind to oxygen.Here,a rudimentary expression of bio-electrochemiluminescent（ECL）macromolecules was achieved via the complexation of zinc proto-porphyrin IX（Zn PPIX）within apo-hemoglobin（apo-Hb）.A high-yield monochromic irradiation at 644 nm could be provoked potentiostatically from the reconstituted holo-Hb^{Zn PPIX} in solutions.Its secondary structure integrity was elucidated by UV and circular dichroism spectrometry,while voltammetry-hyphenated surface plasmon resonance authenticated its ligation conservativeness in electrical fields.Further conjugation with streptavidin rendered a homogenous Janus fusion of both receptor and reporter domains,enabling a new abiological catalyst-linked ECL bioassay.On the other hand,singular Zn PPIX inside each tetrameric subunit of Hb accomplished an overall signal amplification without the bother of luminogenic heterojunctions.This p H-tolerant and non-photobleaching optics was essentialized to be the unique configuration interaction between Zn and O₂,by which the direct electrochemistry of proteins catalyzed the transient progression of O₂→O₂^·-→O₂*+hυselectively.Such principle was implemented as a signal-on strategy for the determination of a characteristic cancer biomarker,the vascular endothelial growth factor,resulting in competent performance at a low detection limit of 0.6pg·m L^-1 and a wide calibration range along with good stability and reliability in real practices.More importantly,its genetically engineered variants may come in handy in biomedical diagnosis and visual electrophysiology.