Dominican amber is the fossil resin famous for the best quality of inclusions, exploited in Dominican Republic from the deposits formed in the late Early Miocene, ca. 16 Ma. A new species, Polymera (Polymera) alexanderi sp. n. of the dipteran family Limoniidae is described from this amber. This new limonid belongs to the genus Polymera Wiedemann, 1820 with 63 extant species described mostly from South America. Only three fossil species are known so far from Dominican and Baltic amber.
While
quantum dots (QDs) are useful as fluorescent labels, their
application in biosciences is limited due to the stability and hydrophobicity
of their surface. In this study, we tested two types of proteins for
use as a cover for spherical QDs, composed of cadmium selenide. Pumilio
homology domain (Puf), which is mostly α-helical, and leucine-rich
repeat (LRR) domain, which is rich in β-sheets, were selected
to determine if there is a preference for one of these secondary structure
types for nanoparticle covers. The protein sequences were optimized
to improve their interaction with the surface of QDs. The solubilization
of the apoproteins and their assembly with nanoparticles required
the application of a detergent, which was removed in subsequent steps.
Finally, only the Puf-based cover was successful enough as a QD hydrophilic
cover. We showed that a single polypeptide dimer of Puf, PufPuf, can
form a cover. We characterized the size and fluorescent properties
of the obtained QD:protein assemblies. We showed that the secondary
structure of the Puf proteins was not destroyed upon contact with
the QDs. We demonstrated that these assemblies do not promote the
formation of reactive oxygen species during illumination of the nanoparticles.
The data represent advances in the effort to obtain a stable biocompatible
cover for QDs.
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