ABSTRACT:The melt-direct intercalation method was employed to prepare poly(propylene) (PP)-maleic anhydride grafted poly(propylene) (PP-g-MAH)-organic-montmorillonite (Org-MMT) nanocomposites. X-ray diffractometry (XRD) was used to investigate the intercalation effect, crystallite size, and crystal cell parameter in these composites. Two kinds of maleated PP, with graft efficiencies of 0.6 and 0.9 wt %, and two sorts of manufacturing processes were used to prepare nanocomposites and then to investigate their effects on intercalation behavior. The results showed that the intercalation effect was enhanced by increasing the content of PP-g-MAH, using maleated PP with higher graft efficiency, and adopting the mold process. The crystallite size of nanocomposites perpendicular to the crystalline plane, such as (040), (130), (111), and (041), reached the minimum value when the content of PP-g-MAH was 20 wt %. This result indicated that the crystallite size of PP in nanocomposites decreased by proper addition of PP-g-MAH. Maximum values in tensile strength (40.2 MPa) and impact strength (24.3 J/m) were achieved when the content of PP-g-MAH was 10 and 20%, respectively.

Summary Controlled stability of proteins is a highly efficient mechanism to direct diverse processes in plants. A key regulatory system for protein stability is given by the CULLIN‐RING E3 ligases (CRLs). In this work, MYB43 is identified as a novel target of a CUL4‐DDB1‐PRL1 (PLEIOTROPIC REGULATORY LOCUS 1)‐RING E3 ligase (CRL4PRL1 E3 ligase). Its stability depends on the presence of PRL1, a WD40‐containing protein functioning as a substrate receptor of the CRL4 E3 ligases. Genetic studies have indicated that MYB43 is a negative regulator of cadmium (Cd) tolerance in Arabidopsis by transcriptional inhibition of important Cd transporters (HMA2, HMA3 and HMA4), while PRL1 and CUL4 positively regulate Cd tolerance. Expression of CUL4 and PRL1 was enhanced in response to Cd stress, and PRL1 can interact with and target MYB43 for degradation depending on assembly of CRL4PRL1 E3 ligase, and consequently increase the expression of HMA2, HMA3 and HMA4 through attenuating the transcriptional inhibition. HMA2 and HMA4 are shown to transport cadmium ion (Cd2+) from the roots of plants to the shoots through the xylem, ultimately increasing the plants’ tolerance to Cd stress.

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