Isomerases are a general class of enzymes that convert a molecule from one isomer to another. Isomerases facilitate intramolecular rearrangements in which bonds are formed; the general form of such a reaction is as follows: A–B → B–A There is only one substrate yielding one product. This product has the same molecular formula as the substrate but differs in bond connectivity or spatial arrangement. Isomerases catalyze reactions across many biological processes, such as in glycolysis and carbohydrate metabolism. Isomerases catalyze changes within one molecule, they convert one isomer to another, meaning that the end product has the same molecular formula but a different physical structure. Isomers themselves exist in many varieties but can be classified as structural isomers or stereoisomers. Structural isomers have a different ordering of bonds and/or different bond connectivity from one another, as in the case of hexane and its four other isomeric forms. Stereoisomers have the same ordering of individual bonds and the same connectivity but the three-dimensional arrangement of bonded atoms differ.
For example, 2-butene exists in two isomeric forms: trans-2-butene. The sub-categories of isomerases containing racemases and cis-trans isomers are examples of enzymes catalyzing the interconversion of stereoisomers. Intramolecular lyases and transferases catalyze the interconversion of structural isomers; the prevalence of each isomer in nature depends in part on the isomerization energy, the difference in energy between isomers. Isomers close in energy can interconvert and are seen in comparable proportions; the isomerization energy, for example, for converting from a stable cis isomer to the less stable trans isomer is greater than for the reverse reaction, explaining why in the absence of isomerases or an outside energy source such as ultraviolet radiation a given cis isomer tends to be present in greater amounts than the trans isomer. Isomerases can increase the reaction rate by lowering the isomerization energy. Calculating isomerase kinetics from experimental data can be more difficult than for other enzymes because the use of product inhibition experiments is impractical.
That is, isomerization is not an irreversible reaction since a reaction vessel will contain one substrate and one product so the typical simplified model for calculating reaction kinetics does not hold. There are practical difficulties in determining the rate-determining step at high concentrations in a single isomerization. Instead, tracer perturbation can overcome these technical difficulties if there are two forms of the unbound enzyme; this technique uses isotope exchange to measure indirectly the interconversion of the free enzyme between its two forms. The radiolabeled substrate and product diffuse in a time-dependent manner; when the system reaches equilibrium the addition of unlabeled substrate unbalances it. As equilibrium is established again, the radiolabeled substrate and product are tracked to determine energetic information; the earliest use of this technique elucidated the kinetics and mechanism underlying the action of phosphoglucomutase, favoring the model of indirect transfer of phosphate with one intermediate and the direct transfer of glucose.
This technique was adopted to study the profile of proline racemase and its two states: the form which isomerizes L-proline and the other for D-proline. At high concentrations it was shown that the transition state in this interconversion is rate-limiting and that these enzyme forms may differ just in the protonation at the acidic and basic groups of the active site. "the names of isomerases are formed as "substrate isomerase", or as "substrate type of isomerase"." Enzyme-catalyzed reactions each have a uniquely assigned classification number. Isomerase-catalyzed reactions have their own EC category: EC 5. Isomerases are further classified into six subclasses: This category includes and epimerases); these isomerases invert stereochemistry at the target chiral carbon. Racemases act upon molecules with one chiral carbon for inversion of stereochemistry, whereas epimerases target molecules with multiple chiral carbons and act upon one of them. A molecule with only one chiral carbon has two enantiomeric forms, such as serine having the isoforms D-serine and L-serine differing only in the absolute configuration about the chiral carbon.
A molecule with multiple chiral carbons has two forms at each chiral carbon. Isomerization at one chiral carbon of several yields epimers, which differ from one another in absolute configuration at just one chiral carbon. For example, D-glucose and D-mannose differ in configuration at just one chiral carbon; this class is further broken down by the group the enzyme acts upon: This category includes enzymes that catalyze the isomerization of cis-trans isomers. Alkenes and cycloalkanes may have cis-trans stereoisomers; these isomers are not distinguished by absolute configuration but rather by the position of substituent groups relative to a plane of reference, as across a double bond or relative to a ring structure. Cis isomers have substituent groups on the same side and trans isomers have groups on opposite sides; this category is not broken down any further. All entries presently include: This category includes intramolecular oxidoreductases; these isomerases catalyze the transfer of electrons from one part of the molecule to another.
The Orchard Hill Observatory is an astronomical observatory located at the highest point on the University of Massachusetts Amherst campus. Constructed in 1965, the observatory is a red brick building with a 16-inch Cassegrain reflector optical telescope, it is used for several community events and is open for public viewing on Thursday nights. The observatory was home to a 20” telescope, given to the department by an avid amateur who lived in central Massachusetts, it was a 1/10 scale model of a larger 200” scope. A crack was spotted during one of the re-aluminizings of the 20” mirror and the scope was no more. In the meantime, the department had been granted money associated with its move from Hasbrouck to the Grad Research Tower to buy a small telescope and put in on top of the GRC; the GRC had a small "isolation" pad built on its roof, supposed to be a mount for the scope, which could be accessed via a small open elevator. However, the GRC had terrible noise and gross vibration problems; the isolation pad never worked and there were too many safety concerns about using the roof of the building for observing.
A 16" telescope was bought from Competition Associates. That scope arrived in 1976 but because of the problems with using the top of the GRC, the scope was never mounted there. In fact, it sat in the basement of Hasbrouck for 10 years, becoming known as the "Subterranean Telescope.” This situation led to the 20" being disassembled and the 16" scope being moved to Orchard Hill and installed in the dome there. The 16" was a major improvement in usability; as to what happened to the 20", the mirror may have been stored in the Astronomy Research Facility but the drive was most not kept. Special thanks to Professor Thomas Arny for much of the recent history of the facility; the observatory does not have a regular schedule. It is operated by the UMass Astronomy Department; the observatory is supported by members of the Five College Astronomy Club. The observatory does not receive any external funding; the program is student-run. It is a part of the College of Natural Sciences/Astronomy, it is possible to see a variety of astronomical bodies at the observatory.
Members of the observatory keep a log online of. Some things that have been logged are the double star Albireo, the great nebula in Andromeda, a dense patch of stars in the milky way near Cygnus, Jupiter with Galilean moons, the waxing gibbous Moon and Alcor & Mizar; the Five College Astronomy Club is a club for those interested in astronomy, regardless of major. The club utilizes the Orchard Hill Observatory to host observing nights on clear Wednesday and Thursday nights; the club travels to other observatories and other sites of interest related to astronomy. The club spans between the Five Colleges to further their experiences and connect with other students who share their interest in astronomy; the club sometimes hosts informational sessions geared towards students looking to propel into research positions or achieve specific academic goals within the astronomy major. However, the main objective of the club is to have fun and meet other people with a shared interest in astronomy. Meets: Thursday Nights at 7:00PM Usually in LGRT 1033 OR Clear Wednesday and Thursday Nights at dusk at the Orchard Hill Observatory Chartered: Fall 2011 The Five College Astronomy Department is a collaborative program of Amherst College, Hampshire College, Mount Holyoke College, Smith College, the University of Massachusetts, which are all located in the Connecticut River valley of western Massachusetts.
Holy Trinity Church is a redundant Anglican church on Low Lane in the village of Wensley, North Yorkshire, England. The building is recorded in the National Heritage List for England as a designated Grade I listed building, is under the care of the Churches Conservation Trust. Alec Clifton-Taylor includes the church in his list of ` best'; the present church dates from the middle of the 13th century, is built on the foundations of an 8th century Saxon church. Additions or alterations were made in the 14th and 15th centuries, the tower was added in 1719. Church records list rectors from 1181 to 2001. For centuries starting in the 1300s, Holy Trinity received support from the owners of Bolton Castle, the Scrope family. A report on this building by the University of London provides the following specifics: "The church dates from about 1240, the south chancel wall being intact of that date; the chancel was of the same size as at present, but the east window and the piscina appear to be somewhat and the north wall of the chancel has evidently been rebuilt upon the old foundations.
The chancel arch and the capitals and bases of the two nave arcades are work of this date. The arcades are unusually lofty; the north vestry, with priest's lodging above, the north and south porches are work of the 15th century. The tower and the west ends of the aisles were rebuilt in the 18th century."Box pews were added in the early 19th century but the medieval character was retained. The two manual pipe organ was installed in 1885; the church was restored in 1927 when the roof was renewed, the whitewash on the walls was removed. This restoration revealed wall paintings depicting Jacob and Esau which were restored as far as possible. Rt. Revd. Lucius Smith, Bishop of Knaresborough re-opened it on 25 January 1928; when the church was vested in the Churches Conservation Trust in 2006 a number of repairs were necessary costing about £125,000. While it is not used for worship, the church remains open to visitors; the church is constructed in stone rubble with sandstone ashlar dressings. The roof is with lead on the chancel and the north porch.
A number of carved Saxon stones are built into the walls. Its plan consists of a nave, with north and south aisles and north and south porches, a chancel with a north vestry, a west tower; the tower has three stages, with buttresses on the bottom stage, a two-light west window. On the south side is a stair turret; the clock was made by W. Potts and Son of Leeds and is dated 1899. In the middle stage there are single-light windows on the west and south faces, a door on the east side, a clock on the north face; the top stage contains two-light bell openings. On the summit, the parapet is plain and there are small obelisks at the corners; the south aisle has a two-light west window. The gabled south porch has diagonal buttresses. Above its opening is a sundial dated 1846. Inside the porch are stone benches; the north porch dates from the 14th century. Above the doorway are coats of arms, it contains stone benches. On the south side of the church are buttresses with three double lancet windows, the middle one of, over a priest's door.
The east window has five lights, on the east gable end is a cross. The vestry on the north side has two storeys. There is a two-light window on each storey. Inside the church is a tower arch, a chancel arch and a three-bay arcade, all dating from the early 14th century; the church is considered to be as notable for its furnishings. In the chancel is a piscina with a trefoil head. On the chancel floor are two brass memorials; the choir stalls have carved ends dated 1527, the communion rail dates from the 17th century. In the tower arch is a 15th-century rood screen; the nave contains the Scrope family pew with a 17th-century front and, at the back is a carved parclose screen from the early 16th century, moved from Easby Abbey at the Dissolution. The nave contains 17th-century benches and box pews from the 18th century, an 18th-century double-decker pulpit, an octagonal font dated 1662 with a cover wooden cover surmounted by a pineapple finial. On the walls are memorials, on the north wall are fragments of medieval wall paintings discovered during 1927-1928.
In the east window of the south aisle are fragments of medieval stained glass. In the church is a royal coat of arms dated 1701, the standard of the Loyal Dales Volunteers. A wooden cupboard in the church is claimed to be a reliquary containing remains of Saint Agatha; the three-manual organ was built by Isaac Abbott of Leeds in memory of Letitia, Baroness Bolton and opened on 19 April 1883, restored by Wood Wordsworth of Leeds. There is a ring of three bells. Two of these were cast in 1725 by Samuel II Smith, the third was cast by Charles and George Mears of the Whitechapel Bell Foundry in 1847. Grade I listed buildings in North Yorkshire List of churches preserved by the Churches Conservation Trust in Northern England "Wensley church- the storywriter's church", Pipspatch.com, personal web site