N-heterocyclic carbenes are of central importance in many domains of chemistry such as organometallic, catalysis and bioinorganic. Their great importance is due to their ability to act as ligands with a large number of transition metals. These Metal-NHCs are used as catalysts in various organic transformations with good biological properties. A wide range of Metals - NHC has been found to be useful as a catalyst in various reactions using Ru, Pd, Ir, Au and Ag. This review examines the different classes of Metal - NHCs and their applications as effective catalysts in several types of organic processes, for example the formation of amide linkage, hydrogenation, isomerization, cycloisomerization, cyclopropanation, hydrosilylation, allylation and desallylation, enol-ester synthesis, heterocycle synthesis, C - C alkyne coupling.

This study was aimed at determining the prevalence estimate and association of transfusion-transmitted infections (TTIs) with ABO and Rh blood groups among blood donors at the King Faisal Specialist Hospital and Research Center (KFSH & RC) in the western region of Saudi Arabia. A retrospective study was conducted at the blood bank center of KFSH and RC from 1 January 2013 to 31 December 2019. Data on ABO and Rh blood group testing, serological testing, molecular investigations, serological assays, nucleic acid testing (NATs), and socio-demographic information were gathered. During the study period, there were 959,431 blood donors at the KFSH and RC. The overall 7-year cumulative prevalence estimate of blood transfusion-transmitted infections among blood donors was low at 7.93%, with an average prevalence estimate of 0.66%. Donors with the O blood group, the O RhD +ve blood group, in particular, were more at risk of developing TTIs, whereas donors with the AB blood group, the AB RhD −ve blood group, in particular, were at the lowest risk of developing TTIs. In total, 96.9% of the blood donors were males (n = 916,567). Almost half of the blood donors belong to the O blood group (49.4%). A total of 861,279 (91.0%) donors were found to be RhD positive. The percentages of TTIs were found to be higher in RhD +ve donors compared with RhD −ve donors. The prevalence estimate of the hemoglobin C (HbC) infection was the most common TTI among the blood donors being 3.97%, followed by malaria being 2.21%. The least prevalence estimate of TTI in the present study was for NAT HIV being 0.02%. Significant associations were observed between RhD +ve and RhD −ve among the malaria-infected donors (A: χ2 = 26.618, p = 0.001; AB: χ2 = 23.540, p = 0.001; B: χ2 = 5.419, p = 0.020; O: χ2 = 68.701, p = 0.001). The current 7-year retrospective study showed a low level of TTIs among blood donors. However, we urge that more research encompassing the entire country be conducted in order to obtain more representative results in terms of the prevalence estimate and association of transfusion-transmitted infections with ABO and Rh blood groups in communities.

Plasminogen activation rates are enhanced by cell surface binding. We have previously demonstrated that exogenous plasminogen binds to phosphatidylserine-exposing and spread platelets. Platelets contain plasminogen in their α-granules but secretion of plasminogen from platelets has not been studied. Recently, a novel transmembrane lysine-dependent plasminogen receptor, Plg-RKT, has been described on macrophages. Here, we analyzed the pool of plasminogen in platelets and examined whether platelets express Plg-RKT. Plasminogen content of the supernatant of resting and collagen/thrombin-stimulated platelets was similar. Pre-treatment with the lysine analogue, εACA, significantly increased platelet-derived plasminogen (0.33 nmol/108 plts vs. 0.08 nmol/108 plts) in the stimulated supernatant, indicating a lysine-dependent mechanism of membrane retention. Lysine-dependent, platelet-derived plasminogen retention on thrombin and convulxin activated human platelets was confirmed by flow cytometry. Platelets initiated fibrinolytic activity in fluorescently labelled plasminogen-deficient clots and in turbidimetric clot lysis assays. A 17 kDa band, consistent with Plg-RKT, was detected in the platelet membrane fraction by Western blotting. Confocal microscopy of stimulated platelets revealed Plg-RKT co-localized with platelet-derived plasminogen on the activated platelet membrane. Plasminogen exposure was significantly attenuated in thrombin and convulxin stimulated platelets from Plg-RKT-/- mice compared to Plg-RKT+/+ littermates. Membrane exposure of Plg-RKT was not dependent on plasminogen, as similar levels of the receptor were detected in plasminogen-/- platelets. These data highlight Plg-RKT as a novel plasminogen receptor in human and murine platelets. We show for the first time that platelet-derived plasminogen is retained on the activated platelet membrane and drives local fibrinolysis, by enhancing cell-surface mediated plasminogen activation.

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