RESUMO
The novel heptanuclear cadmium borovanadate [Cd(en)3]{[Cd(H2O)(en)]6[B20V12O60(OH)2]}·8H2O (en = ethylenediamine) has been prepared under hydrothermal condition. It exhibits a 2D layered architecture that is built up from the [Cd(H2O)(en)]2+ coordination cations and new sandwich-type borovanadate anions [B20V12O60(OH)2]14- constructed by BO3, BO4, BO3(OH), and VO5 units. It features the first heptanuclear cadmium borovanadate containing the single valence of V4+ cations and unique B/V ratio (B/V = 20/12). Its thermal, magnetic, XPS, and optical properties have been systematically studied. The Eg (2.60 eV), EVB (1.69 eV), and ECB (-0.91 eV) were well determined by the UV-vis diffuse reflectance spectrum, UPS curve, and the formula ECB = EVB - Eg, respectively. The photocatalytic experiments revealed that the borovanadate could be selected as an effective and stable heterogeneous catalyst for the reduction of CO2 to CH4 by means of visible light (the amount for CH4 gas could reach 50.57 µmol·g-1·h-1 when the reaction time was 3 h). The recycling experiment and photocatalytic mechanism were also well investigated and established in detail.
RESUMO
Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) restricts platelet activation via platelet collagen receptor GPVI/FcRγ-chain. In this study, screening against collagen-induced platelet aggregation was performed to identify functional CEACAM1 extracellular domain fragments. CEACAM1 fragments, including Ala-substituted peptides, were synthesized. Platelet assays were conducted on healthy donor samples for aggregation, cytotoxicity, adhesion, spreading, and secretion. Mice were used for tail bleeding and FeCl3-induced thrombosis experiments. Clot retraction was assessed using platelet-rich plasma. Extracellular segments of CEACAM1 and A1 domain-derived peptide QDTT were identified, while N, A2, and B domains showed no involvement. QDTT inhibited platelet aggregation. Ala substitution for essential amino acids (Asp139, Thr141, Tyr142, Trp144, and Trp145) in the QDTT sequence abrogated collagen-induced aggregation inhibition. QDTT also suppressed platelet secretion and "inside-out" GP IIb/IIIa activation by convulxin, along with inhibiting PI3K/Akt pathways. QDTT curtailed FeCl3-induced mesenteric thrombosis without significantly prolonging bleeding time, implying the potential of CEACAM1 A1 domain against platelet activation without raising bleeding risk, thus paving the way for novel antiplatelet drugs.
What is the context? The study focuses on Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) and its role in platelet activation, particularly through the GPVI/FcRγ-chain pathway.The research aims to identify specific fragments of CEACAM1's extracellular domain that could restrict platelet activation, without increasing bleeding risk.What is new? The researchers identified a peptide called QDTT derived from the A1 domain of CEACAM1's extracellular segment. This peptide demonstrated the ability to inhibit platelet aggregation, secretion, and GP IIb/IIIa activation.The study also revealed that specific amino acids within the QDTT sequence were essential for its inhibitory effects on collagen-induced aggregation.What is the impact? The findings suggest that the A1 domain-derived peptide QDTT from CEACAM1 could serve as a potential basis for developing novel antiplatelet drugs. This peptide effectively limits platelet activation and aggregation without significantly prolonging bleeding time, indicating a promising approach to managing thrombosis and related disorders while minimizing bleeding risks.