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Ribbon diagram of dihydrofolate reductase

Enzyme kinetics is the study of the rates of enzyme-catalysed chemical reactions where the reaction rate is measured and the effects of varying the conditions of the reaction are investigated. The study of an enzyme's kinetics can reveal the catalytic mechanism of the enzyme, its role in metabolism, how its activity is controlled, and how a modifier might affect the rate. Some enzymes change shape significantly during the mechanism; in such cases, it is helpful to determine the enzyme structure with and without bound substrate analogues that do not undergo the enzymatic reaction. When enzymes bind multiple substrates, enzyme kinetics can show the sequence in which these substrates bind and determine the sequence in which products are released. There is typically one rate-determining step that determines the overall kinetics, which may be a chemical reaction or a conformational change of the enzyme or substrates. (Full article...)

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Madalitso Baloyi

... that Madalitso Baloyi (pictured), Malawi's minister of health, pretended to be a patient at a hospital in Lilongwe?
... that a critic compared the way in which the protagonist of a 1975 Turkish short story isolated himself out of fear to the COVID-19 lockdowns?
... that Madeline Woo, a San Francisco Ballet principal dancer, has tattoos but covers them for performances?
... that a Hawaii TV station telecast a football game as a favor to the state's dying former governor?
... that Aria Bolkus, the daughter of a former government minister, was elected to the South Australian House of Assembly three months after her father's death?
... that a character's outfit from the anime The Executioner and Her Way of Life was inspired by Clint Eastwood's spaghetti Western roles?
... that Fedor Karzhavin may have stolen the charter of the College of William & Mary?
... that the Forest Service Road System is eight times the length of the Interstate Highway System?
... that, after 13-year-old King Henry I of Castile was fatally struck by a tile dislodged by a playmate, his guardian tried to hide his death?

In the news

Rumen Radev

The Progressive Bulgaria coalition, led by former president Rumen Radev (pictured), wins a majority of the National Assembly in the parliamentary election, in a bid to end the ongoing Bulgarian political crisis.
In Ukraine, seven people are killed and fourteen others are injured in a mass shooting at a Kyiv supermarket.
Separate school shootings in Siverek and in Onikişubat, Turkey, leave 12 people dead and 35 others injured.
Romuald Wadagni wins the Beninese presidential election.

On this day

April 27: Koningsdag in the Netherlands

Für Elise

395 – Aelia Eudoxia married Byzantine emperor Arcadius without the knowledge or consent of Rufinus, the Praetorian prefect who had intended for his own daughter to wed the emperor.
1810 – Ludwig van Beethoven composed his Bagatelle No. 25 in A minor, better known as "Für Elise" (audio featured), one of his most popular compositions.
1961 – Prime Minister Milton Margai led the Sierra Leone Colony and Protectorate to independence from the United Kingdom.
1997 – American spree killer Andrew Cunanan murdered Jeffrey Trail, a former friend and a Gulf War veteran, who became the first victim of Cunanan's killing spree.

Mary Wollstonecraft (b. 1759)
Margaret Macpherson Grant (b. 1834)
Basil A. Paterson (b. 1926)
Cristian Romero (b. 1998)

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Kirby logo

The Kirby video game series is a franchise of platform games and other genres (including puzzle and racing games) published and produced by Nintendo. The games have been developed by Japan-based HAL Laboratory, a Nintendo second-party developer. All Kirby video games have been developed exclusively for Nintendo video game consoles and handhelds dating from the Nintendo Entertainment System to the eighth generation of video game consoles. The series debuted in Japan on April 27, 1992, with Hoshi no Kirby, which later was released in the North American and PAL regions in August 1992 as Kirby's Dream Land. (Full list...)

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Episyrphus balteatus, sometimes called the marmalade hoverfly, is a relatively small hoverfly (9 to 12 mm; 0.35 to 0.47 in), in the family Syrphidae. It is widespread throughout the Palearctic region, which covers Europe, North Asia and North Africa, and is considered to be the most abundant native hoverfly in Central Europe. The upper side of its abdomen is patterned with orange and black bands, which may appear wasp-like to other animals, such as birds, protecting it from predation – an example of Batesian mimicry. It can be found throughout the year in various habitats, including urban gardens, visiting flowers for pollen and nectar. This male E. balteatus hoverfly was photographed on a valerian in Wengen, Switzerland.

Photograph credit: Charles J. Sharp

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