Manganese, requirements

A study of the role of base and ligand in the isomerization of manganese-coordinated conjugated alkynyl carbonyls to the corresponding allenyl carbonyls shows that manganese requires a ligand prior to isomerization with amine bases and the efficacy of these bases correlates with p Ka (Scheme 97). Potassium /-buloxide led to rapid isomerization in the absence of added ligand.140... 

The manganese balance of ten 6-day old breast-fed infants was measured for a 3-day period by Widdowson in 1969 (20). For a 3.5 kg infant, an intake of 7 (ig/day produced a negative balance of 31 ig. Alexander et al. (8) studied the manganese requirements of children, 3 months to 9 years, fed normal and synthetic diets. From calculation of their data, a manganese intake of 1.15 mg/day in a 20 kg child would produce a positive retention of 0.16 mg. 

Studies of manganese requirements in humans are complicated by the fact that excretion, rather than absorption, is believed to be the major regulator of homeostatic control. Britton and Cotzias (41) fed diets containing varying levels of manganese to... 

Two human studies have reported increased, but not significant, losses of fecal manganese in subjects when dietary levels of phosphorus were increased from 800 to 1,500 mg (30) and from 1,010 to 2,525 mg/day (31). In animals, elevated dietary levels of phosphorus have been reported to increase manganese requirements (51) however, the dietary level of calcium in this study was also high. 

In 1940, Basu and Malakar (22) first recommended a manganese requirement for adults to range from 3.7 to 5.5 mg/day, based on fecal excretions that were near positive balances. In 1949, De (23) calculated a lower requirement, 2.74 mg, using regression analysis of manganese balance. However, no diets were fed near this level. More recently, Rao and Rao have estimated adult requirements to be 3.72 mg (34) and 4.15 mg (33) per day based on consumption of Indian foods. 

Mg and Ca, and, while Co is a competitive inhibitor, other transition metals are not taken up by this pathway. Mn may also be cotransported with citrate, while low affinity mechanisms are also known. Despite the demonstration of these pathways it is difficult to demonstrate manganese requirements for growth in many cases. 

Now, suppose that while working in chemistry lab, you need 3.00 moles of manganese (Mn) for a chemical reaction. How can you measure that amount Like the 5 dozen jellybeans, the number of moles of manganese can be converted to an equivalent mass and measured on a balance. To calculate mass from the number of moles, you need to multiply the number of moles of manganese required in the reaction (3.00 moles of Mn) by a conversion factor that relates mass and moles of manganese. That conversion factor is the molar mass of manganese (54.9 g/mol). 

C Eyster, TE Brown, HA Tanner and SL Hood (1958) Manganese requirement with respect to growth, Hill reaction and photosynthesis. Plant Physiol 33 235-241... 

MT Moreira, G Feijoo, R Sierra-Alvarez, JA Field. Reevaluation of the manganese requirement for the biobleaching of kraft pulp by white rot fungi. Bioresour Technol 70(3) 255-260, 1999. 

Children, like adults, are primarily exposed to manganese through the food they eat. The human diet typically provides the amount of manganese required for the normal functioning of a healthy body. Children, like adults, can also inhale manganese if it is present in the air. 

---