This article aims to encourage practitioners, young and seasoned, by enhancing their structure-determination toolboxes with a selection of tips and tricks on recognizing and handling aspects of data collection, structure modelling and refinement, and the interpretation of results.

In small-molecule single-crystal structure determination, we now have at our disposal an inspiring range of fantastic diffractometers with better, brighter sources, and faster, more sensitive detectors. Faster and more powerful computers provide integrated tools and software with impressive graphical user interfaces. Yet these tools can lead to the temptation not to check the work thoroughly and one can too easily overlook tell-tale signs that something might be amiss in a structure determination; validation with checkCIF is not always revealing. This article aims to encourage practitioners, young and seasoned, by enhancing their structure-determination toolboxes with a selection tips and tricks on recognizing and handling aspects that one should constantly be aware of. Topics include a pitfall when setting up data collections, the usefulness of reciprocal lattice layer images, processing twinned data, tips for disorder modelling and the use of restraints, ensuring hydrogen atoms are added to a model correctly, validation beyond checkCIF, and the derivation and interpretation of the final results.

The positional change of nitro­gen-7 of the RNA constituent guanosine to the bridgehead position-5 leads to the base-modified nucleoside 5-aza-7-de­aza­guanosine. Contrary to guanosine, this mol­ecule cannot form Hoogsteen base pairs and the Watson–Crick proton donor site N3—H becomes a proton-acceptor site. This causes changes in nucleobase recognition in nucleic acids and has been used to construct stable `all-purine' DNA and DNA with silver-mediated base pairs. The present work reports the single-crystal X-ray structure of 7-iodo-5-aza-7-de­aza­guanosine, C10H12IN5O5 (1). The iodinated nucleoside shows an anti conformation at the glycosylic bond and an N conformation (O4'-endo) for the ribose moiety, with an anti­periplanar orientation of the 5'-hy­droxy group. Crystal packing is controlled by inter­actions between nucleobase and sugar moieties. The 7-iodo substituent forms a contact to oxygen-2' of the ribose moiety. Self-pairing of the nucleobases does not take place. A Hirshfeld surface analysis of 1 highlights the contacts of the nucleobase and sugar moiety (O—H⋯O and N—H⋯O). The concept of pK-value differences to evaluate base-pair stability was applied to purine–purine base pairing and stable base pairs were predicted for the construction of `all-purine' RNA. Furthermore, the 7-iodo substituent of 1 was functionalized with benzo­furan to detect motional constraints by fluorescence spectroscopy.

During evaporation of natural and synthetic K–Mg–Cl brines, the formation of almost square plate-like crystals of potassium carnallite (potassium chloride magnesium dichloride hexa­hydrate) was observed. A single-crystal structure analysis revealed a monoclinic cell [a = 9.251 (2), b = 9.516 (2), c = 13.217 (4) Å, β = 90.06 (2)° and space group C2/c]. The structure is isomorphous with other carnallite-type com­pounds, such as NH4Cl·MgCl2·6H2O. Until now, natural and synthetic carnallite, KCl·MgCl2·6H2O, was only known in its ortho­rhom­bic form [a = 16.0780 (3), b = 22.3850 (5), c = 9.5422 (2) Å and space group Pnna].

A method is adapted to generate a full rank realization of an abstract regular polyhedron with automorphism group H3.

Georgi Dimchev
Apr 9, 2020; 133:jcs239020-jcs239020
Articles

A new report from the National Academies of Sciences, Engineering, and Medicine outlines a research agenda for improving the commercial viability of technologies that turn greenhouse gases from the burning of fossil fuels into useful products such as fuels, construction materials, and chemicals.

At colleges and universities around the nation, scientists and graduate students are seeking out ways to bring their knowledge, skills, and resources to bear in the struggle against COVID-19.

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Opera singer Plácido Domingo, shown here speaking in Spain last July, said earlier this month that he tested positive for the coronavirus.; Credit: Ricardo Rubio/Europa Press via Getty Images

Plácido Domingo has been hospitalized because of COVID-19-related complications, according to multiple reports.

He is in stable condition in an Acapulco, Mexico, hospital and will receive medical attention for "as long as the doctors find it necessary until a hoped-for full recovery," a spokesperson for Domingo told Opera News over the weekend.

Domingo's reported hospitalization comes just days after he posted a March 22 message on Facebook revealing that he had tested positive for the disease caused by the coronavirus.

"I feel it is my moral duty to announce that I tested positive for COVID19, also known as the Corona Virus. My family and I are and will remain individually isolated for as long as it is medically necessary. Today we all enjoyed good health, but I presented symptoms of coughing and fever, so I decided to take the test and the result was positive," Domingo said.

Domingo has been one of opera's most reliable and bankable stars and is known for his ability to sing tenor and baritone and in multiple languages, including Italian, English, Russian and Spanish.

Recently, the 79-year-old has been embroiled in controversy as several women accused the Spanish-born singer of sexual misconduct.

On March 10, NPR reported that LA Opera, which Domingo helped establish, announced that its investigation substantiated 10 "inappropriate conduct" claims levied against him dating back to as early as 1986. Domingo resigned as the LA Opera's general director in October.

Prior to that, he withdrew from a production of the Metropolitan Opera's performance of "Macbeth" amid allegations of sexual misconduct.

He has denied the allegations.

Domingo is among a growing list of celebrities who have announced they have tested positive for the coronavirus, including actor Tom Hanks and his wife Rita Wilson, actor Idris Elba, NBA star Kevin Durant, talk show host Andy Cohen and British Prime Minister Boris Johnson.

This content is from Southern California Public Radio. View the original story at SCPR.org.

Supreme Court Justice Ruth Bader Ginsburg poses for the official photo at the Supreme Court in Washington, D.C. in 2018.; Credit: Mandel Ngan/AFP via Getty Images

Supreme Court Justice Ruth Bader Ginsburg underwent non-surgical treatment Tuesday for a benign gallbladder condition, according to a press release from the Supreme Court. She plans to participate in oral arguments from the hospital on Wednesday, according to the release.

In pain on Monday, Ginsburg went to Sibley Memorial Hospital in Washington after hearing the first-ever Supreme Court teleconference of oral arguments. At Sibley, she was diagnosed with acute cholecystitis, a condition in which a gallstone migrates to the cystic duct. She nonetheless participated in arguments from home on Tuesday, but was in enough pain that she went to Johns Hopkins Hospital in Baltimore for treatment of the infected duct later Tuesday.

Doctors not involved in Ginsburg's care said non-surgical treatment typically involves antibiotics and insertion of a tube to drain the infected duct.

Friends said the justice was in good spirits on Tuesday night, and watching the Metropolitan Opera on her iPad.

Ginsburg's emergency treatment coincides with the U.S. Supreme Court's historic live-streaming of its oral arguments in which the justices are participating by telephone because of the coronavirus. According to the court statement, Ginsburg, 87, is "resting comfortably" and plans to participate in oral arguments again on Wednesday when the court considers an important birth control case.

She is expected to remain in the hospital for another day or two.

Last year, Ginsburg completed three weeks of radiation treatment after a cancerous tumor was discovered on her pancreas. It was the fourth time in 20 years that she had been treated for cancer, and the second time in a year. In December 2019, she was operated on for lung cancer.

This content is from Southern California Public Radio. View the original story at SCPR.org.

Jiro's Pick this week is joyPlot by Santiago Benito.I must admit that I was simply drawn by the visualization, rather than the name of the function, as I was not familiar with the band or the music... read more >>

Director Eliza Hittman on the set of her film "Never Rarely Sometimes Always".
; Credit: Focus Features/Never Rarely Sometimes Always (2020)

The film “Never Rarely Sometimes Always” was slated for a theatrical release in March, but due to COVID-19 screenings were postponed. Instead, the film is out on digital this week, currently sporting a 98 percent rating on Rotten Tomatoes and receiving critical acclaim both here on FilmWeek and nationwide as one of the best films of 2020 so far.

Writer-director Eliza Hittman’s third feature-length film is about two teenage girls Skylar (Talia Ryder) and Autumn (Sidney Flanagan) from rural Pennsylvania who travel to New York City for medical help after an unplanned pregnancy. Hittman says the idea for the film came to her when she read in a book about how some women in Ireland, which up until recently had very strict laws against abortions, would travel from Ireland to London in 24 hours just to get a procedure. It struck her as worthy of a screenplay, and the idea was born. As part of her research for the film Hittman went to a small coal-mining community in rural Pennsylvania and, even though she wasn’t pregnant, visited pregnancy centers, got tested, and talked with women getting treatment and counseling so she could, as she says, “write the scenes with credibility.”

Today on FilmWeek, we’ll air “The Frame” host John Horn’s interview with “Never Rarely Sometimes Always” director Eliza Hittman where the two discuss how Hittman came up with the idea for the film, her journey to rural America to find out what visiting pregnancy centers there is like, and how that informed the way she conceived and wrote the film.

Guest:

Eliza Hittman, writer and director of “Never Rarely Sometimes Always”

This content is from Southern California Public Radio. View the original story at SCPR.org.

Hispanic Mexican city of Teotihuacan may have bred rabbits and hares for food, fur and bone tools, according to a study published August 17, 2016 in the open-access journal PLOS ONE by Andrew Somerville from the University of California San Diego, US, and colleagues.

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