There’s nothing new or unusual about corporate and academic collaboration. IBM, for instance, has partnered with universities around the country since the 1940s to support computer science education. This relationship is mutually beneficial both for the tech giant and the institutions sponsored. IBM’s grant dollars provide welcome funding for research and equipment for students, all while fostering a new class of computer scientists and engineers.

University-business partnerships, however, require a careful balance. Take the tobacco industry. According to a 2012 study by Harvard professor Allan Brandt, cigarette makers all but invented the concept of industry-academic conflicts of interest. Since the 1950s, cigarette companies have sought to influence the debate about the dangers of smoking to sell more of their products. One tactic used was aligning with university-based science and underwriting millions of dollars for favorable research.

A number of industries have evidently taken a page from the tobacco playbook. Powerful industries from Big Oil to Big Food have been found funneling eye-popping sums of money to university professors in order to fund research and promote their commercial interests. The corporate hijacking of higher education is more complex than it looks. When state universities or land grant colleges see their budgets stretched thin, some faculty may feel pressured to seek or accept much-needed funding in ways that are not transparent to the public.

Nonetheless, academics are counted upon for the integrity of their assertions. Industry funding has been shown to undermine objectivity, and professors violate their responsibilities as impartial experts as well as the public’s trust when they associate with unscrupulous commercial interests.

Here are 13 prominent university professors who appear to have stepped over the line between big business and academia.

1 & 2. Carol O’Neil & Theresa Nicklas. Back in 2011, a number of media outlets breathlessly touted a surprising new study that found children who eat candy weigh less than children who do not. The study’s authors included professors O'Neil of Louisiana State University and Nicklas of Baylor College of Medicine and Victor Fulgoni, a former Kellogg executive and consultant.

Unsurprisingly, an Associated Press investigation by Candice Choi revealed that paper was not only partially sponsored by the National Confectioners Association—which counts such candy giants as Hershey, Wrigley, Mars and Nestle as group members—but that the trade group also made a number of suggestions to the paper. "You'll note I took most but not (all) their comments," Fulgoni wrote in an email to O'Neil in 2010. A similar study on candy and adults also received comments from the candy group.

O'Neil told the AP she did not receive compensation for the work, but in 2011, Nicklas sent Nutrition Impact, Fulgoni’s consulting business, an invoice for $11,500 for three manuscripts, including $2,500 for "candy." The professors also co-authored a paper about the health benefits of chickpeas and hummus funded by Sabra Dipping Co. Even though a disclosure said that Sabra did not provide input, the final paper did include the company’s suggestions, the AP reported.

3. Wei-Hock Soon. The aerospace engineer at the Harvard-Smithsonian Center for Astrophysics is a noted climate change skeptic, who asserts that global warming is caused by the sun, not human activity. Freedom of Information Act documents obtained by Greenpeace showed that Soon accepted more than $1 million over the last decade from fossil fuel titans such as Exxon Mobil, the American Petroleum Institute, the Koch brothers and more.

The New York Times reported that Soon failed to disclose that conflict of interest in his scientific papers at least 11 times. This is also telling: His work is often cited by prominent climate-denying politicians, including snowball-wielding Senator James Inhofe (R-OK), the chairman of the Senate Committee on the Environment and Public Works who considers Soon one of his personal heroes.

Soon still passionately defends his work and presented his research at a Paris Climate Conference “counter-conference” alongside Heartland Institute, the Committee for a Constructive Tomorrow and the Competitive Enterprise Institute.

Watch the video below:

4. William Happer. In December, a bombshell Greenpeace sting suggested that two academics from prominent universities could be bought by fossil fuel companies. The first was Happer, a Princeton University professor and prominent climate change skeptic. The physicist, who is not a climatologist, was approached by Greenpeace activists posing as consultants of a Beirut-based energy company to author a paper on “the benefits of carbon dioxide from fossil fuels.”

Emails show that Happer wanted $250 an hour for his work and asked that his fee be paid to the climate-doubting group CO2 Coalition, where he’s a board member. Happer also disclosed in the emails that Peabody Energy donated $8,000 to the CO2 Coalition for testimony in a Minnesota hearing on the impacts of carbon dioxide.

The Greenpeace investigation was released hours before Happer testified at Sen. Ted Cruz’s (R-Tex.) bizarre Senate hearing disputing climate change. Right before his testimony, when a Greenpeace researcher confronted Happer about how much money he received from Peabody, Happer barked, “You son of a bitch, I haven’t taken a dime!”

Happer has not disputed the veracity of the emails but refused to comment about the operation.

Watch here:

5. Frank Clemente. The professor emeritus of sociology at Penn State University was the second professor implicated by the Greenpeace operation. This time, Greenpeace activists posed as Indonesian coal mining representatives and approached Clemente to write a report before the Paris Climate talks “to counter damaging research on linking coal to premature deaths,” according to published emails. Clemente, who has previously argued against coal divestment among educational institutions, agreed and requested $15,000 for an 8- to 10-page report and emphasized he would not have to disclose his sponsor.

“There is no requirement to declare source funding in the US,” Clemente wrote in an email. “My research and writing has been supported by government agencies, trade associations, the university and private companies and all has been published under the rubric of me as an independent scholar—which I am.”

In response, Clemente told the Australian Broadcasting Corporation he was an independent consultant and not on the Penn State payroll during the sting. “I fully stand behind every single statement I made,” he said.

6. Bruce Chassy. Like Soon, the University of Illinois professor emeritus has similarly come under fire for his close ties to the controversial agrichemical industry. U.S. Right to Know, a nonprofit watchdog group, obtained a jaw-dropping cache of emails through FOIA requests unveiling how Monsanto and its allies not only donated money to professors but also enlisted them to do PR, lobbying and regulatory work for the agrichemical industry.

On September 2015, a stunning exposÃ© from the New York Times on the FOIA emails described how Chassy received money from Monsanto and collaborated with the agrichemical industry’s lobbying of the U.S. Environmental Protection Agency to reject a proposal that would tighten the regulations on pesticide-resistant seeds.

Monsanto’s Eric Sachs, who leads the company’s scientific outreach, emailed Chassy to set up Academics Review, a nonprofit aimed at countering critics of GMOs. “The key” to Academics Review’s success will be “keeping Monsanto in the background so as not to harm the credibility of the information,” Sachs wrote.

This past March, a WBEZ investigation by Monica Eng uncovered that Monsanto gave Chassy more than $57,000 in two years to help promote, defend and deregulate GMOs through the lobbying of federal officials. Monsanto also made $140,000 in “biotech research and outreach” payments through the University of Illinois Foundation between 2006 and June 2012.

Chassy has harshly criticized the U.S. Right to Know campaign.

7. Kevin Folta. The professor and chairman of the horticultural sciences department at the University of Florida has been labeled a “Monsanto shill” by critics after the FOIA emails indicated frequent collaboration with the world’s largest seed company. The plant scientist was the center of the 2015 New York Times exposÃ© by Eric Lipton, who writes:

Dr. Folta, the emails show, soon became part of an inner circle of industry consultants, lobbyists and executives who devised strategy on how to block state efforts to mandate G.M.O. labeling and, most recently, on how to get Congress to pass legislation that would pre-empt any state from taking such a step.

“I’m glad to sign on to whatever you like, or write whatever you like,” Folta wrote in an October 2014 email to a Monsanto executive.

Folta, a Buzzfeed profile noted, corresponded with global public relations firm Ketchum, which represents the powerful Council for Biotechnology Information, to write an Orlando Sentinel op-ed, in which he claims "profiting authors, celebrity chefs and eco-terrorists" are attempting "to arrest the pace of scientific progress" in regard to GMOs. (Ketchum has a notorious reputation: Stacy Malkan, the co-director of U.S. Right to Know, notes that the firm "remains a key player in PR efforts to dampen demand for organic foods, spinning messages that tell consumers organics are over-priced and over-hyped… [and] runs the GMO Answers website, funded by Monsanto, Dow, DuPont, Syngenta, Bayer and BASF.")

In August 2014, Monsanto gave Folta an unrestricted $25,000 grant through the university’s agricultural biotechnology communication program. The university tried returning the money to Monsanto, but the company refused. Folta, citing personal threats, later decided to donate the money to a campus food bank. Folta wrote in a recent blog post that he is neither pro- nor anti-GMO but has an “overwhelmingly positive” opinion of the technology.

8. David Shaw. According to the New York Times piece, Monsanto provided at least $880,000 in grants to Mississippi State University’s vice president for research and economic development.

The FOIA emails show that Shaw was approached by both Monsanto and Dow Chemical to submit comments to the USDA to approve the former’s Roundup Ready 2 Xtend GMO soybeans and the latter’s Enlist weedkiller. Dow executive Larry Walton sent a June 2015 email to Shaw requesting his support for Enlist. In the message, Walton noted that the Mississippi Agricultural Industry Council, where Walton is president, has provided scholarship funds to Mississippi State students. Shaw agreed to the two requests.

Shaw, Folta and seven other professors were also included in an August 2013 group email from Sachs, the Monsanto outreach executive. Sachs asks the group to lend their academic gravitas on a series of articles touting the benefits of GMOs aimed at the general public. The Monsanto exec even assigned them topics and provided talking points and added that company-hired PR firms would plug the finished articles.

“The key to success is participation by all of you—recognized leaders with the knowledge, reputation and communication experience needed to communicate authoritatively with the target groups,” the email stated.

Shaw and Cornell entomologist and professor Anthony Shelton were tasked with the topic, “sustainable crop systems” and the professors complied. The final co-authored article, “Green Genes: Sustainability Advantages of Herbicide Tolerant and Insect Resistant Crops,” was published by the Genetic Literacy Project, an organization critics have labeled an agrichemical industry front group.

9. Calestous Juma. The Harvard University’s Kennedy School of Government professor was also part of the Sachs group email. Juma, who is enthusiastically pro-GMO, wrote a December 2014 piece titled, “Global Risks of Rejecting Agricultural Biotechnology,” a topic—and a similar headline—Sachs suggested. The piece was also published by the Genetic Literacy Project.

Citing the FOIA emails, the Boston Globe described how Monsanto connected Juma with a marketing company to promote his paper “as part of Monsanto’s strategy to win over the public and lawmakers.” The international development specialist defended his piece, telling the Boston Globe he was not paid by Monsanto and merely pulled material from his previously published book on the topic.

“It’s not that I was trying to hide anything,” Juma said.

10. James O. Hill. The University of Colorado professor of pediatrics and medicine was the former president of the Global Energy Balance Network, a nonprofit that promoted itself as a obesity research nonprofit. ExposÃ©s from the Associated Press and the New York Times in 2015, however, revealed that Coca-Cola was funding research that claims lack of exercise, not sugary soda, is to blame for the global obesity epidemic. According to the Associated Press, since 2010, the beverage giant gave $1 million to the University of Colorado School of Medicine, and since 2010, $550,000 to Hill.

While the group denied its research was influenced by Coke, Hill wrote in an email to a top Coke executive, "I want to help your company avoid the image of being a problem in people's' lives and back to being a company that brings important and fun things to them.” The network disbanded in late 2015, citing “resource limitations.”

11. Steven N. Blair. As the New York Times described in its 2015 report, the University of South Carolina public health professor—“whose research over the past 25 years has formed much of the basis of federal guidelines on physical activity”—was the vice president of the Global Energy Balance Network. The University of South Carolina also received, and kept $500,000 from Coke.

In a video launching the Global Energy Balance Network, Blair said, “Most of the focus in the popular media and in the scientific press is, ‘Oh they’re eating too much, eating too much, eating too much’—blaming fast food, blaming sugary drinks and so on. And there’s really virtually no compelling evidence that that, in fact, is the cause.”

But as AlterNet's Reynard Loki reported, the 2010 Dietary Guidelines for Americans, a joint report of the U.S. Departments of Agriculture and Health and Human Services found that "sugary beverages are extremely popular, with soda, energy drinks and sports drinks making up the fourth highest source of calories among Americans overall—and the third highest source for children and adolescents up to the age of 18."

12. Gregory A. Hand. The former founding dean and professor of epidemiology at West Virginia University School of Public Health also helped found the Global Energy Balance Network. Hand, along with professors Hill and Blair, announcing the group’s formation in the British Journal of Sports Medicine. According to the New York Times, Coca-Cola gave Hand $806,500 in 2011 for a study and another $507,000 in 2014 to establish the group. Hand’s CV from August 2015 boasts funding from the Coca-Cola Company.

Hand’s colleague, Walter Willett, chair of the Nutrition Department at the Harvard School of Public Health likened the actions of the Global Energy Balance Network to the tobacco industry’s campaign to downplay the health risks of smoking. “You can always buy somebody, it seems,” Willett told the Charleston Gazette-Mail. “And it’s really unfortunate that some members of our academic community essentially go on the payroll of Coca-Cola, either directly or indirectly.”

News emerged this month that Hand has been forced out as dean. He has been demoted to a role “in developing partnerships that enhance the mission and work of health sciences at WVU,” the school is quoted as saying, according to Corporate Crime Reporter.

13. Peter Phillips. The University of Saskatchewan public policy professor was also asked by Monsanto's Eric Sachs to throw his weight behind a pro-GMO piece.

The finished piece, “Economic Consequences of Regulations of GM Crops,” closely mirrored the subject matter of “burdensome” regulations that stifle biotechnology, something that Sachs had pitched. The paper was again published on the Genetic Literacy Project website in December and did not disclose Monsanto’s meddling.

According to the Saskatoon StarPhoenix, “Phillips said there was no need to declare his connections because he was not paid and Monsanto did not ask him to alter his research.”

However, Gary Ruskin, co-director for U.S Right to Know which accessed the emails, disagrees.

“Monsanto says jump and these scientists said, how high? This is not how publicly funded scientists should behave,” Ruskin told the publication, adding that Americans should trust top university scientists to disclose any conflict of interest.