Dalton, Howard

Howard Dalton was born in New Malden, Surrey , February 8, 1944; the son of Leslie Alfred Dalton, a truck driver, and Florence Gertrude Dalton (née Evans). Graduated from Rains Park High School.

He graduated from the University of Sussex with a doctorate for defending work in a nitrogen fixation laboratory ^[4] .

After defending his doctoral dissertation, he left for a short period in the United States to build his scientific career at the University of Warwick.

He devoted his life to studying the process of methane oxidation by bacteria, using this relatively inert gas as their sole source of carbon and energy. Howard discovered two completely new multicomponent monooxygenase enzymes responsible for the initial oxidation of methane to methanol. Then he continued to study their functions, mechanisms, regulation and structures. The great specificity of their substrate led to its interest in using these and related enzymes for biocatalysis, biological transformations, and bioremediation.

While working at the University of Warwick, he was also the chief scientific adviser to the UK government at the Department of the Environment and Agriculture (Defra).

He was also an activist in the protest movement against the Vietnam War.

Realizing that EPR spectroscopic methods will be of great importance in the study of metalloproteins, Howard returned to Sussex University in 1970 to work with Dr. Bob Brey at the Department of Chemistry on two molybdenum-containing enzymes, reductase nitrate from Aspergillus nidulans fungi and xanthine dehydrogenase Veles from xanthine . He used the EPR to study the chemical environment of their molybdenum cofactors, as well as their flavins and centers of iron-sulfur, providing an understanding of the mechanism of action of the enzyme and the separation of electrons between cofactors in the enzyme.

In October 1971, Howard married Cyrus Rostislavovna de Armitt Rozhdestvenskaya, the daughter of Rostislav Sergeyevich Rozhdestvensky, a college professor.

In the early 1970s, Derek Burke opened the Department of Biological Sciences at the University of Warwick and appointed Roger Whittenbury as head of the department to become the founder of microbiology there in 1972. A year later, Howard was appointed lecturer to the department to increase his knowledge of microbial biochemistry and physiology in 1973, and then he and his wife Kira moved to the village of Radford Semele, near Leamington Spa. This led to his long and very successful tenure at the University of Warwick, during which his studies earned him a well-deserved international reputation, produced many successful publications in his scientific career, creating more than 200 articles, and even opening up new areas of research in the microbiology of monocarbon compounds (C1).

Throughout the 1980s and 1990s, Howard gradually created and led the microbiology research team at the Department of Biological Sciences in Warwick, until it became one of the largest of its kind in the UK, covering multidisciplinary research in microbiology, often with an applied bias . Following the retirement of Roger Whittenbury, Howard became chair of the Department of Biological Sciences in 1999 and was an effective and popular leader there until he was seconded to Defra in 2002.

From March 2002 to September 2007, Howard worked as Chief Scientific Advisor at Defra. He was the department’s first chief scientific adviser appointed by the Sir David King of the Fed, who at that time was the prime minister’s chief scientific adviser. Over the next five years, Howard improved Defroy's use of science, striving to teach its employees how to make strong decisions based on sound scientific evidence. Howard led the science advisory group, setting up the UK emergency response plan for the bird flu virus, and played an important role in raising climate change as a serious threat by lecturing on these and other topics, such as biofuels and genetically modified crops, on many national and international meetings.

Tennis was a great passion, and he was a member of the Leamington Real Tennis Club, where he had the championship in many tournaments. It was on one of them, playing in a friendly doubles tournament, that he suddenly fainted and died. This happened on January 12, 2008.

Nitrogen Fixation Research

Howard's research career began with a doctoral dissertation at the University of Sussex under the direction of Professor John Postgate (a member of the Royal Society since 1977) on an nitrogen fixation arc unit. He studied nitrogen fixation in aerobic soil nitrogen bacteria. This doctoral dissertation was defended in 1968. During bacterial nitrogen fixation, atmospheric nitrogen is reduced to ammonia in a reaction catalyzed by a nitrogenase complex, which consists of two proteins containing metals such as iron and molybdenum. The high sensitivity of this enzyme to oxygen formed the basis of the main question of Dalton's doctoral dissertation: how does oxygen-sensitive nitrogenase act in bacteria in a highly aerobic environment? His extensive, creative study clearly showed that this problem can be explained by two mechanisms: firstly, respiratory protection, in which breathing was used to blow oxygen down to safe levels, and secondly, conformational protection, wherein changes in the conformation of the enzyme protect sites sensitive to oxygen ^[5] .

In 1968, Dalton moved to the United States for two years to collaborate with Professor Lan Mortensen at Purdue University, Indiana, to study the biochemistry of nitrogenase in the anaerobic bacteria Clostridium. This work expanded his knowledge in protein purification, spectrophotometric analysis, and electron paramagnetic resonance (EPR) spectroscopy of metal enzymes in complex multiprotein systems. These studies contributed to the development of his subsequent work on methane oxidation.

Research on Methane Oxidation

Methylotrophs are microbes that can grow on reduced carbon compounds containing one or more carbon atoms but not containing carbon-carbon bonds; examples of such substances are methane, methanol, methylamine and trimethylamine ^[6] . The end product of all anaerobic microbial degradation of organic material is methane. Part of it reaches the atmosphere, where it is a powerful greenhouse gas. Methanotrophs are the main group of methylotrophs capable of using methane and, therefore, play an important role in the carbon cycle, reducing the amount of methane released into the atmosphere. They have become important because they can be used in the processes of biotransformation and bioremediation. Methanotrophs are divided into type I and type II ^[7] . Initially, this separation was based on their internal membrane systems, but the types of methanotrophs also differ in their methods of carbon assimilation, genetic systems, phylogeny, etc.

Howard assembled a large research team at the University of Warwick and directed a work on an extremely complex process in which methane is oxidized to methanol when exposed to mitotrophs. This is the first necessary step for the subsequent production of energy and the assimilation of carbon in new cells. All the energy used for the growth of methanotrophs is generated during the oxidation of methane to carbon dioxide:

CH ₄ → CH ₃ OH → HCHO → HCOOH → CO ₂ .

In 1973, the first stage of this process was practically not studied. Dalton decided to start his study, using the data obtained when working on multicomponent metal-containing enzyme systems, which he received during his study of nitrogenase and related enzymes. He successfully achieved his goal with research students and professors, most notably John Colby and David Sterling. The joint work of many laboratories using various methanotrophs led to a general conclusion: the first stage of methane oxidation is catalyzed by a mixed monooxygenase system. This is now called methane monooxygenase (MMO); it is she who hydroxylates methane to methanol using molecular oxygen and a reducing agent (AH ₂ ):

CH ₄ + AH ₂ + O ₂ → CH ₃ OH + H ₂ O + A.

The reducing agent was supposed to be the usual metabolic reducing agent, NADH or NADPH, but in earlier studies there was considerable confusion and disagreement between these results, which was often associated with the use of various bacteria, membrane preparations, and enzyme assays. Explicit assay systems would include spectrophotometric measurement of the disappearance of NADH, or methane-dependent and NADH-dependent oxygen consumption. However, most cell-free preparations use membrane fractions containing NADH oxidase, which also consumes NADH and oxygen, and the methanol product can also be further metabolized.

Dalton's essential first step in solving the problem was the development of reliable, unambiguous analysis systems; The systems he created are still in use. They do not use an obvious substrate (methane), but they are based on the use of alternative alkanes, the oxidation of which MMO depended on its exceptionally broad substrate specificity ^[8] . These methods include the oxidation of bromomethane, the disappearance of which can be measured by gas-liquid chromatography (GLC), and the oxidation of ethylene or propylene, and epoxy products are also measured by GLC.

Discovery of methane monooxygenase

The application of these methods led to the final description of IMO using an enzyme purified from soluble extracts of methanotrophs of type I Methylococcus capsulatus strain Bata. It was originally isolated by Roger Whittenbury from the hot springs of the Roman baths in Bath. Subsequently, this soluble MMO (sMMO) was present in several methanotrophs. The study showed that it catalyzes the hydroxylation of methane to methanol, with NAD (P) H as a reducing agent. It consists of three components and, like nitrogenase, contains metal ions. The decomposition of this enzyme into its constituent proteins was a significant achievement, since only one of the components could be analyzed independently of the other two. This component C is now known as reductase, a flavoprotein containing FAD, and the center of iron sulfide, which is found in spinach ferredoxin and putidaredoxin. Component A is hydroxylase and contains non-hemoglobin iron. Protein binding component B is a small, colorless protein.

Component C transfers electrons from the NADH donor to hydroxylase, which catalyzes the methane substrate using molecular oxygen. Around the same time, John Higgs and his colleagues were able to do the work of partially purifying the three-component IMO ^[9] from the membranes of type II methanotroph, methylosinus trichosporium. The electron donor in untreated preparations was NADH, but ascorbate or cytochrome component C had to be used in purified preparations. The resulting enzyme is relatively unstable, as a result of which some results are not always easy to reproduce. Thus, it seemed that there could be two different types of MMOs or that in both types of methanotroph there could be one membrane MMO with the condition that it could be more easily released from its bond with the membranes to produce sMMOs.

This confusion was ultimately resolved by the Dalton team in a study using the cultivation of a strain of bacteria. It has been shown that there are two completely different enzymes in Methylococcus capsulatus in sMMO, as well as membrane (or partial) IMO (pMMO). The type of enzyme produced depends on the presence of copper: pMMO is formed when the copper: biomass ratio is high, while sMMO is formed when the copper: biomass ratio is low ^[10] . In the group of bacterial cultures, both MMOs can be produced, since the copper: biomass ratio cannot be as controlled or determined (studying the role of copper in methanotrophs ^[11] .).

Subsequently, the Dalton group developed reproducible solubilization and purification methods and showed that the membrane-bound pMMO enzyme also has three components, and also that two types of MMO are present in other methanotrophs regardless of the type of membrane. Some methanotrophs synthesize only one type of MMO, in which case a membrane enzyme is most often formed. It is noteworthy that the two MMO families have no detectable similarities in the amino acid sequence or three-dimensional structure.

A distinctive feature of IMO, possibly related to their normal small non-functionalized methane substrate, is their extremely broad substrate specificity. So sMMO has a wider range of substrates than pMMO. Substrates for sMMOs include H-alkanes, H-alkenes, chloromethane, bromomethane, trichloromethane, nitromethane, methanol, carbon monoxide, dimethyl ether, benzene, styrene and pyridine ^[12] . This enzyme is capable of oxidizing ammonia, whose structure is clearly similar to that of methane.

When whole cells are used, a reducing agent must also be provided in addition to the potential substrate (e.g. methanol or formate). In some cases, the oxidation of a potential substrate is called co-oxidation.

Dalton showed that since methanotrophs can co-oxidize a number of hydrocarbons and chlorinated pollutants, they are of biotechnological interest, far beyond their ability to oxidize methane to methanol ^[13] . Important examples are the industrial production of methanol from methane, the co-oxidation of propene to epoxypropane, the bioremediation of chlorinated hydrocarbons and the production of valuable recombinant proteins using methane as starting material.

Howard's interest in biotransformations and his knowledge in this area helped him become a consultant to New Jersey Celanese, and then joined the scientific advisory board for spin biotechnology company Celgene, where he continued to study the chemical and industrial aspects of microbiology.

Research on oxidative enzymes for use in future use in biotransformation

The wide substrate specificity of methane monooxygenases made it possible to use them as catalysts for complex chemical reactions that could lead to useful materials. Although Howard Dalton's earlier work in Warwick was largely based on methane monooxygenases, after 1986 he was more concerned with the study of other types of oxidoreductases. His main colleague in these studies was Derek Boyd from Queen's University of Belfast. Their fruitful cooperation in the field of chemical microbiology lasted 20 years. At the same time, their work received joint awards from British research Councils, programs of the European Union, as well as industry, which financed all projects for chemical catalytic synthesis in Warwick and Belfast.

Howard Dalton, together with Derek Boyd, published 42 joint publications and created 3 patents.

At the beginning of their collaboration in 1986, they decided that, since the demand for chiral synthons is increasing both in the academic and industrial fields, the important goals of their research should include:

1. Development of reliable methods for the distribution of the structure and stereochemistry of metabolites,
2. The discovery of new types of metabolites of cis and trans dihydrodiol,
3. Investigation of potentially competing reactions catalyzed by toluene dioxygenase,
4. Evaluation of new uses of chiral metabolites in chemical synthesis, including chiral ligands.

Most biotransformations were carried out and analyzed at the University of Warwick, after which they were transported to the University of Belfast for chemical analysis.

Further studies of Howard's methane monooxygenase have been developed in collaboration with other scientists.

After purification and characterization of the two main types of methane monooxygenase, the main problem was the molecular biology of their synthesis and regulation. This aspect was reviewed and developed in the Howard department by Colin Murrell ^[14] . Another important task was to explain their mechanisms and three-dimensional structures.

The structure of the soluble enzyme was mainly determined by the group of the scientist Lippard ^[15] .

In 1983, the School of Biological Sciences established a degree in microbiology and microbial technology, and Howard, together with his former graduate student Colin Murrell, who returned to the department the same year as a teacher, played an important role in developing this innovative course, one of the first in its kind in the UK. Its popularity increased over the next 10 years, preparing a new generation of microbiologists who were familiar with the use of microbes (especially methanotrophs) in the field of biotechnology.

In 1980, Rod Quayle and his colleagues organized a symposium in Sheffield, where Howard edited his scientific papers ^[16] . 12 years later, together with his colleagues from the department, he was responsible for the seventh symposium held at the University of Warwick ^[17] . Howard greatly changed the organization of these symposia with his direct scientific contribution to them.

Dalton held a number of positions at the university, dealing with both academic issues and other areas of university life. He was the leader of more than 100 graduate and doctoral students. Howard was also a teacher, especially popular with bachelors, and his witty style inspired many students to study microbiology and pursue a career in this field after graduation.

Dalton sponsored his own village youth football team.

Howard was awarded a personal presidency in Warwick in 1983.

In 1993, Howard was elected a member of the Royal Society, and in 2000 he was awarded the Levenguk Medal and Lecture, which was created to award outstanding scientists in the field of microbiology; his lecture was entitled "The Natural and Unnatural History of Methane-Oxidizing Bacteria." From 2007 to 2008, he was president of the Marine Biological Association, and from 1997 to 2000, he was president of the Society of General Microbiology. He was named a knight-bachelor in the list of honors students of 2007 for his services to science.

His colleague in the Department of Defra Helen Ghosh has established a new award for Sports Day - the Howard Dalton Trophy.

In 2010, Defra also organized an inaugural event for Howard Dalton's annual lecture.

Also, through communication with senior people in the UK and America, Howard was able to receive large donations to complete the project to build a medical center in Yappin; It is currently named after the Howard Dalton Clinic and is supported by generous donations.

In addition, the council of the Society of General Microbiology decided to rename the competition "Young Microbiologist of the Year" in honor of Sir Howard, whose prize now is the Sir Howard Dalton Prize and a scholarship.

Howard was married to Kira Rostislavovna de Armitt Rozhdestvenskaya, daughter of Rostislav Sergeyevich Rozhdestvensky, a college professor. In marriage, they had two children: Amber and Jed.

After the death of her husband, Kirado still lives in Workshire in the summer, spending the rest of his time working on an African oyster farm in The Gambia. Daughter Amber lives in Peckham with her husband and two children, Huxley Howard and Ines; She works as a magazine editor and restaurant critic, and also organizes tasting events for dishes and wines. Jed's son lives in Escher with his wife and their children, Rosie, Henry and Ajay; he runs a company that provides software consulting services to energy companies. In his free time, he also enjoys playing tennis at Hampton Court.

Howard was a good scientist, practical, confident person, sociable and witty, inspiring colleagues who, most often, ridiculed science.

A cheerful, sociable person, he gladly joined the American culture, often arranging friendly gatherings for his colleagues, for example, parties with Super Bowls.

In the 1980s, he was the "first celebrity" at meetings of bioscience workers in Warwick at weekly meetings at local pubs.

Sometimes he liked to play "poker night" with some colleagues.

Howard was interested in Japanese gardens and even created two such gardens at the University of Warwick.

He was a fan of the Tottenham Hotspur football club (Spurs). In addition, he was a member of the football team of biological sciences. In the 1970s, Howard distinguished himself by playing on the Biohazard team in a friendly match with the Saudi team.

He also loved village cricket.

Real tennis was a great passion, and he was a member of the Leamington Real Tennis Club, where he had the championship in many tournaments.

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