Information:  - Antifolates are a class of antimetabolite medications that antagonise (that is, block) the actions of folic acid (vitamin B). Folic acid's primary function in the body is as a cofactor to various methyltransferases involved in serine, methionine, thymidine and purine biosynthesis. Consequently, antifolates inhibit cell division, DNA/RNA synthesis and repair and protein synthesis. Some such as proguanil, pyrimethamine and trimethoprim selectively inhibit folate's actions in microbial organisms such as bacteria, protozoa and fungi. The majority of antifolates work by inhibiting dihydrofolate reductase (DHFR).  - Cycloguanil is a dihydrofolate reductase inhibitor , and is a metabolite of the antimalarial drug proguanil ; its formation in vivo has been thought to be primarily responsible for the antimalarial activity of proguanil . However , more recent work has indicated that , while proguanil is synergistic with the drug atovaquone ( as in the combination Malarone ) , cycloguanil is in fact antagonistic to the effects of atovaquone , suggesting that , unlike cycloguanil , proguanil may have an alternative mechanism of antimalarial action besides dihydrofolate reductase inhibition . Although cycloguanil is not currently in general use as an antimalarial , the continuing development of resistance to current antimalarial drugs has led to renewed interest in studying the use of cycloguanil in combination with other drugs .  - Dihydrofolate reductase, or DHFR, is an enzyme that reduces dihydrofolic acid to tetrahydrofolic acid, using NADPH as electron donor, which can be converted to the kinds of tetrahydrofolate cofactors used in 1-carbon transfer chemistry. In humans, the DHFR enzyme is encoded by the "DHFR" gene. It is found in the q11q22 region of chromosome 5. Bacterial species possess distinct DHFR enzymes (based on their pattern of binding diaminoheterocyclic molecules), but mammalian DHFRs are highly similar.  - A dihydrofolate reductase inhibitor (DHFR inhibitor) is a molecule that inhibits the function of dihydrofolate reductase, and is a type of antifolate.  - Atovaquone (alternative spelling: atavaquone) is a chemical compound that belongs to the class of naphthoquinones. Atovaquone is a hydroxy-1,4-naphthoquinone, an analog of ubiquinone, with antipneumocystic activity. It is manufactured in the US in the liquid form, or oral suspension, under the brand name Mepron.    Given the information above, choose from the list below the object entity that exhibits the relation 'instance of' with the subject 'cycloguanil'.  Choices: - activity  - brand  - chemical compound  - class  - dna  - electron  - enzyme  - function  - gene  - humans  - liquid  - molecule  - species  - vitamin  - work
chemical compound

Information:  - The 12th Pan American Games were held in Mar del Plata, Argentina, from March 12 to March 26, 1995. After 44 years, this was the Pan American Games first return to the country that hosted the first Games, in 1951.  - Argentina, officially the Argentine Republic, is a federal republic in the southern half of South America. Sharing the bulk of the Southern Cone with its neighbor Chile to the west, the country is also bordered by Bolivia and Paraguay to the north, Brazil to the northeast, Uruguay and the South Atlantic Ocean to the east, and the Drake Passage to the south. With a mainland area of , Argentina is the eighth-largest country in the world, the second largest in Latin America, and the largest Spanish-speaking one. The country is subdivided into twenty-three provinces (singular "provincia") and one autonomous city ("ciudad autónoma"), Buenos Aires, which is the federal capital of the nation as decided by Congress. The provinces and the capital have their own constitutions, but exist under a federal system.  - The Pan-American or Pan American Games (also known colloquially as the Pan Am Games) is a major sporting event in the Americas featuring summer sports, in which thousands of athletes participate in a variety of competitions. The competition is held among athletes from nations of the Americas, every four years in the year before the Summer Olympic Games. The only Winter Pan American Games were held in 1990. The Pan American Sports Organization (PASO) is the governing body of the Pan American Games movement, whose structure and actions are defined by the Olympic Charter.  - This page shows the results of the Judo Competition for men and women at the 1995 Pan American Games , held from March 11 to March 26 in Mar del Plata , Argentina . There were eight weight divisions .  - Mar del Plata is an Argentine city in the southeast part of Buenos Aires Province located on the coast of the Atlantic Ocean. It is the head of General Pueyrredón Partido. Mar del Plata is the second largest city in Buenos Aires Province. The name "Mar del Plata" has the meaning of "sea of the Plate region" or "adjoining sea to the (River) Plate region". Mar del Plata is one of the major fishing ports and the biggest seaside beach resort in Argentina. With a population of 614,350 as per the , it is the 7th largest city in Argentina.    Given the information above, choose from the list below the object entity that exhibits the relation 'instance of' with the subject 'judo at the 1995 pan american games'.  Choices: - buenos aires  - city  - competition  - congress  - country  - del  - event  - federal republic  - four  - governing body  - march  - name  - ocean  - organization  - pan american games  - plate  - population  - republic  - resort  - river  - sea  - sharing  - sports organization  - structure  - three  - variety
event