In chemistry, a disulfide refers to a functional group with the structure R−S−S−R′. The linkage is called an SS-bond or sometimes a disulfide bridge and is derived by the coupling of two thiol groups. In biology, disulfide bridges formed between thiol groups in two cysteine residues are an important component of the secondary and tertiary structure of proteins; the connection is a persulfide, in analogy to its congener, but this terminology is used, except in reference to hydrodisulfides. In inorganic chemistry disulfide refers to the corresponding anion S2−2. Symmetrical disulfides are compounds of the formula R2S2. Most disulfides encountered in organo sulfur chemistry are symmetrical. Unsymmetrical disulfides are compounds of the formula RSSR', they are less common in organic chemistry. The disulfide bonds are strong, with a typical bond dissociation energy of 60 kcal/mol. However, being about 40% weaker than C−C and C−H bonds, the disulfide bond is the "weak link" in many molecules. Furthermore, reflecting the polarizability of divalent sulfur, the S−S bond is susceptible to scission by polar reagents, both electrophiles and nucleophiles: RS−SR + Nu− → RS−Nu + RS−The disulfide bond is about 2.05 Å in length, about 0.5 Å longer than a C−C bond.
Rotation about the S−S axis is subject to a low barrier. Disulfides show a distinct preference for dihedral angles approaching 90°; when the angle approaches 0° or 180° the disulfide is a better oxidant. Disulfides where the two R groups are the same are called symmetric, examples being diphenyl disulfide and dimethyl disulfide; when the two R groups are not identical, the compound is said to be an asymmetric or mixed disulfide. Although the hydrogenation of disulfides is not practical, the equilibrium constant for the reaction provides a measure of the standard redox potential for disulfides: RSSR + H2 → 2 RSHThis value is about −250 mV versus the standard hydrogen electrode. By comparison, the standard reduction potential for ferrodoxins is about −430 mV. Disulfide bonds are formed from the oxidation of sulfhydryl groups in biological contexts; the transformation is depicted as follows: 2 RSH ⇌ RS−SR + 2 H+ + 2 e−A variety of oxidants participate in this reaction including oxygen and hydrogen peroxide.
Such reactions are thought to proceed via sulfenic acid intermediates. In the laboratory, iodine in the presence of base is employed to oxidize thiols to disulfides. Several metals, such as copper and iron complexes affect this reaction. Alternatively, disulfide bonds in proteins formed by thiol-disulfide exchange: RS−SR + R′SH ⇌ R′S−SR + RSHSuch reactions are mediated by enzymes in some cases and in other cases are under equilibrium control in the presence of a catalytic amount of base; the alkylation of alkali metal di- and polysulfides gives disulfides. "Thiokol" polymers arise. In the converse reaction, carbanionic reagents react with elemental sulfur to afford mixtures of the thioether and higher polysulfides; these reactions are unselective but can be optimized for specific applications. Many specialized methods have been developed for forming unsymmetrical disulfides. Reagents that deliver the equivalent of "RS+" react with thiols to give asymmetrical disulfides: RSH + R′SNR″2 → RS−SR′ + HNR″2where R″2N is the phthalimido group.
Bunte salts, derivatives of the type RSSO3–Na+ are used to generate unsymmetrical disulfides: Na + NaSR' → RSSR' + Na2SO3 The most important aspect of disulfide bonds is their cleavage, which occurs via reduction. A variety of reductants can be used. In biochemistry, thiols such as β-mercaptoethanol or dithiothreitol serve as reductants. Furthermore, it is not needed to remove TCEP before modification of protein thiols. In organic synthesis, hydride agents are employed for scission of disulfides, such as sodium borohydride. More aggressive, alkali metals will effect this reaction: RS−SR + 2 Na → 2 NaSRThese reactions are followed by protonation of the resulting metal thiolate: NaSR + HCl → HSR + NaClThiol–disulfide exchange is a chemical reaction in which a thiolate group −S− attacks a sulfur atom of a disulfide bond −S−S−; the original disulfide bond is broken, its other sulfur atom is released as a new thiolate, carrying away the negative charge. Meanwhile, a new disulfide bond forms between the original sulfur atom.
Thiolates, not thiols, attack disulfide bonds. Hence, thiol–disulfide exchange is inhibited at low pH where the protonated thiol form is favored relative to the deprotonated thiolate form. Thiol–disulfide exchange is the principal reaction by which disulfide bonds are formed and rearranged in a protein; the rearrangement of disulfide bonds within a protein occurs via intra-protein thiol–disulfide exchange reactions. This process of disulfide rearrangement does
William Lanman Bull Sr. was an American banker who served as president of the New York Stock Exchange. Bull was born on August 1844, in New York City, he was the seventh youngest son of Frederic Bull and Mary Huntington Bull. Among his siblings were Elizabeth Atwater Bull, Frederic Bull, Anna Chester Bull, his paternal grandparent were Elizabeth Bull and Jireh Bull and his maternal grandparents were Peter Lanman and Abigail Lanman. Through his mother, he was a first cousin of scholar Charles Rockwell Lanman. After receiving a preparatory education, he studied at the College of the City of New York, where he graduated in 1864. After graduation, Bull began his business career by joining Edward Sweet & Co. a banking house founded in 1854 where his brother-in-law was the senior partner. In 1867, he became a position he held uninterruptedly for over forty-five years; the prominent firm became known as "a Vanderbilt and Rockefeller house" and E. H. Harriman did business for the firm when he was a broker.
Bull served as a director of several companies, including the Northern Pacific Railway, the East Tennessee and Georgia Railway, the New York and Western Railway, the Atchison and Santa Fe Railway. In 1869, Bull joined the New York Stock Exchange and was "one of fifty brokers who secured his membership for $1,000 a piece when the Stock Exchange was consolidated with the gold board." He became a member of the Exchange's board of governors and in May 1888, he was elected president of the Exchange, served two terms until he was succeeded by Watson B. Dickerman in 1890, he retired from business in 1908. Shortly after his death, Edward Sweet & Co., at 34 Pine Street, was dissolved and its business taken over by Chandler Brothers & Co. of New York and Philadelphia. Sweet partner Lewis E. Waring became a partner in Chandler, although his fellow partners Frederic Bull and Louis Livingston did not. On February 15, 1871, Bull was married to Sara Newton "Tasie" Worthington. Tasie was the daughter of prominent businessman and inventor Henry Rossiter Worthington and Sara Jane Worthington.
Together, they resided at 805 Fifth Avenue and were the parents of: Frederic Bull, who married his second cousin, Mary Helen Robinson in 1895. They divorced on December 2, 1926, six days he married Susan Fish Dresser, daughter of D. LeRoy Dresser and niece of Edith Stuyvesant Gerry. After her death, he married Corinne Strange, a widow of Albert Bruton Strange, in 1938. Henry Worthington Bull, who married Maud Maria Livingston, a daughter of Robert Cambridge Livingston and Maria Livingston, in 1904, her niece, Phyllis Livingston Potter, was the wife of Fred Astaire. William Lanman Bull Jr. who married Matilda E. Heppenheimer, a daughter of Otto Heppenheimer, in 1904, he was a member of the Chamber of Commerce, the Society of Mayflower Descendants, the American Museum of Natural History, the Metropolitan Museum of Art, the New-York Historical Society, the Sons of the American Revolution, the New York Zoological Society. He was affiliated with the Century Association, Grolier Club, Union Club, Metropolitan Club, Republican Club, Ardsley Club, Church Club, City Club, Midday Club, Alpha Delta Phi, Manhattan Society, the Phi Beta Kappa honorary fraternity.
Bull died of heart disease on January 1914, at his residence in New York. After a funeral at Grace Church, he was buried in the family vault in Green-Wood Cemetery in Brooklyn. William Lanman Bull at Find a Grave
Thrillist is an online media website covering food, drink and entertainment. The company is based in New York City, United States. In October 2016, Thrillist merged with internet brands The Dodo, NowThis News, Seeker to form the digital media holding company Group Nine Media. Thrillist was founded in 2004 by Ben Lerer, son of media executive Kenneth Lerer, Adam Rich, his friend from college, they moved to New York City. Rich served as President, Ben Robinson served as the Chief Creative Officer. Lerer and Rich sent the first Thrillist e-mail newsletter in 2005 to 600 friends. In early 2017, following layoffs of more than 25 employees, the Thrillist editorial and distribution staffs announced plans to unionize with the Writers Guild of America East. In response, Lerer refused to voluntarily recognize and held anti-union, captive audience meetings despite more than 85% of the editorial staff having signed union cards. In July 2017, Thrillist hired entertainment industry veteran and former MTV and GoPro executive Ocean MacAdams to lead the digital brand.
In late September 2018, after more than a year at the bargaining table and a staff walkout, the Thrillist Union and management reached a collective bargaining agreement. The deal included a guaranteed 8.5% raise for all employees in its first year, as well as a salary floor of $50,000/year. "This represents a victory not just for the editorial employees of Thrillist, but for our entire industry," the Thrillist Union's bargaining committee said of the contract. "Through collective action we've made our workplace better and helped set a standard we hope other digital media shops can follow." In May 2010, Thrillist acquired online men's fashion retailer JackThreads. In March 2011, TMG hired Eric Ashman as Chief Financial Officer from The Huffington Post. In 2012, Ashman was charged with committing accounting fraud by the SEC while working as CFO at The Street and was "barred from acting as a director or officer of a public company for three years." In February 2012, Lerer announced the creation of the Thrillist Media Group, which combined Thrillist, deal site Thrillist Rewards, JackThreads.
In August 2012, the media group led a $13 million fundraising round, from OAK, the Pilot Group, Lerer Ventures. In March 2013, TMG discontinued Thrillist Rewards, citing slow growth, launched The Crosby Press, a site designed to market JackThreads products by providing content aimed at a target audience of men in their late teens to early twenties. By May 2015, The Crosby Press had been closed by TMG. In October 2013, TMG launched the tech site Supercompressor, which focused on gear and gadgets for a young male audience. Supercompressor was discontinued as a site in September 2015. In September 2015, TMG announced it raised $54 million in total from European publisher Axel Springer, Oak Investment Partners and SBNY; as part of the transaction, Thrillist separated its businesses, with Thrillist Media group operating the media site, while the e-commerce company operated JackThreads. In October 2016, TMG merged with The Dodo, NowThis Seeker to form Group Nine Media; the newly formed holding company received a $100 million strategic investment from Inc..
In February 2017, JackThreads laid off most of its staff in preparation to "cease operations as an independent company." A number of customers subsequently experienced problems with returns, canceled orders, items that never shipped. Official website