Tailored Tolane-Perfluorotolane Assembly as Supramolecular Base Pair Replacement in DNA.

Arene-fluoroarene interactions offer outstanding possibilities for engineering of supramolecular systems, including nucleic acids. Here, we implement the tolane-perfluorotolane interaction as base pair replacement in DNA. Tolane (THH) and perfluorotolane (TFF) moieties were connected to acyclic backbone units, comprising glycol nucleic acid (GNA) or butyl nucleic acid (BuNA) building blocks, that were incorporated via phosphoramidite chemistry at opposite positions in a DNA duplex. Thermodynamic analyses by UV thermal melting revealed a compelling stabilization by THH/TFF heteropairs only when connected to the BuNA backbone, but not with the shorter GNA linker. Detailed NMR studies confirmed the preference of the BuNA backbone for enhanced polar π-stacking. This work defines how orthogonal supramolecular interactions can be tailored by small constitutional changes in the DNA backbone, and it inspires future studies of arene-fluoroarene-programmed assembly of DNA.

Rapid, convenient and efficient kit-independent detection of SARS-CoV-2 RNA.

Pandemic SARS-CoV-2 infection has rapidly developed into a socioeconomic and humanitarian catastrophe. Basic principles to prevent SARS-CoV-2 transmission are social distancing, face masks, contact tracing and early detection of SARS-CoV-2. To meet these requirements, virtually unlimited test capacities delivering results in a rapid and reliable manner are a prerequisite. Here, we provide and validate such a rapid, convenient and efficient kit-independent detection of SARS-CoV-2 RNA, termed COVID-quick-DET. This straightforward method operates with simple proteinase K treatment and repetitive heating steps with a sensitivity of 94.6% in head-to-head comparisons with kit-based isolation methods. This result is supported by data obtained from serially diluted SARS-CoV-2 virus stocks. Given its cost- and time-effective operation, COVID-quick-DET might be best suited for countries with general shortage or temporary acute scarcity of resources and equipment.

N6 -Isopentenyladenosine in RNA Determines the Cleavage Site of Endonuclease Deoxyribozymes.

RNA-cleaving deoxyribozymes can serve as selective sensors and catalysts to examine the modification state of RNA. However, site-specific endonuclease deoxyribozymes that selectively cleave post-transcriptionally modified RNA are extremely rare and their specificity over unmodified RNA is low. We report that the native tRNA modification N6 -isopentenyladenosine (i6 A) strongly enhances the specificity and has the power to reconfigure the active site of an RNA-cleaving deoxyribozyme. Using in vitro selection, we identified a DNA enzyme that cleaves i6 A-modified RNA at least 2500-fold faster than unmodified RNA. Another deoxyribozyme shows unique and unprecedented behaviour by shifting its cleavage site in the presence of the i6 A RNA modification. Together with deoxyribozymes that are strongly inhibited by i6 A, these results highlight that post-transcriptional RNA modifications modulate the catalytic activity of DNA in various intricate ways.

Fast breakthrough of resistant cytomegalovirus during secondary letermovir prophylaxis in a hematopoietic stem cell transplant recipient.

BACKGROUND: The compound letermovir (LMV) has recently been approved for the prophylaxis of cytomegalovirus (CMV) infection and disease in adult CMV seropositive recipients of an allogeneic hematopoietic stem cell transplant. LMV inhibits CMV replication by binding to the viral terminase complex. However, first cases of clinical LMV resistance have been occurred. Here we report a fast breakthrough of resistant cytomegalovirus during secondary LMV prophylaxis in a hematopoietic-cell transplant recipient. CASE PRESENTATION: A 44-year-old male patient with acute myeloid leukemia (AML) experienced a CMV-reactivation within the first 4 weeks of allogeneic hematopoietic-cell transplantation. Administration of LMV was initiated at day + 34. Due to increasing viral loads, LMV treatment was discontinued after 8 days. The patient was then administered with valganciclovir (valGCV) until viral DNA was undetectable. Due to neutropenia, valGCV treatment was switched to LMV secondary prophylaxis. For 4 weeks, the patient maintain virologic suppression. Then, CMV viral loads increased with a fast kinetic. Genotypic testing of the viral polymerase UL54, the kinase UL97 as well as the viral terminase UL56 and UL89 revealed the mutation C325Y in UL56, which is associated with the high level LMV resistance. CONCLUSION: It is known that Letermovir is approved for prophylactic purposes. However, it may be used for some patients with CMV infection who either have failed prior therapies or are unable to tolerate other anti-CMV compounds. Particularly, the administration of LMV should be avoided in patients with detectable viral loads. When this is not possible, viral load must be routinely monitored along with UL56 genotyping. Furthermore, LMV administration at high virus loads may foster the rapid selection of resistant CMV mutants.

Semen inhibits Zika virus infection of cells and tissues from the anogenital region.

Zika virus (ZIKV) causes severe birth defects and can be transmitted via sexual intercourse. Semen from ZIKV-infected individuals contains high viral loads and may therefore serve as an important vector for virus transmission. Here we analyze the effect of semen on ZIKV infection of cells and tissues derived from the anogenital region. ZIKV replicates in all analyzed cell lines, primary cells, and endometrial or vaginal tissues. However, in the presence of semen, infection by ZIKV and other flaviviruses is potently inhibited. We show that semen prevents ZIKV attachment to target cells, and that an extracellular vesicle preparation from semen is responsible for this anti-ZIKV activity. Our findings suggest that ZIKV transmission is limited by semen. As such, semen appears to serve as a protector against sexual ZIKV transmission, despite the availability of highly susceptible cells in the anogenital tract and high viral loads in this bodily fluid.

Ancistroheynine B and two further 7,3'-coupled naphthylisoquinoline alkaloids from Ancistrocladus heyneanus Wall.

A new axially chiral naphthylisoquinoline alkaloid, ancistroheynine B (7), has been isolated from the leaves of the Indian liana Ancistrocladus heyneanus Wall., along with two known related alkaloids, ancistrocladidine (3) and ancistrotanzanine C (6), which are 7,3'-coupled, too. The structural elucidation was achieved by chemical, spectroscopic, and chiroptical methods. Biological activities of ancistroheynine B against the pathogens of malaria, leishmaniasis, Chagas' disease, and African sleeping sickness were evaluated.

Ancistrolikokine D, a 5,8'-coupled naphthylisoquinoline alkaloid, and related natural products from Ancistrocladus likoko.

A new naphthylisoquinoline alkaloid, ancistrolikokine D, and the likewise 5,8'-coupled alkaloid ancistroealaine A, as well as two further, biosynthetically related, but nitrogen-free natural products, ancistronaphthoic acid B and cis-isoshinanolone, have been isolated from Ancistrocladus likoko J. LEACUTE;ONARD (Ancistrocladaceae). The 5,8'-coupling of the new alkaloids and of the alkaloids isolated earlier hints at a close phylogenetic relationship of A. likoko to other Central African Ancistrocladus species. The compounds show moderate activities against Leishmania donovani, Trypanosoma cruzi, and Trypanosoma brucei rhodesiense.