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Differences were observed in the extent of thermal inactivation of human butyrylcholinesterase (BuChE) and eel acetylcholinesterase (AChE). BuChE was more resistant to 57 degrees C inactivation than was AChE. Thermal inactivation of BuChE was reversible and followed first-order kinetics. AChE thermal inactivation was irreversible and did not follow first-order kinetics. AChE was marginally protected from thermal inactivation by the "nonspecific salts" ammonium sulfate and sodium chloride and to a greater extent by the "active site-specific salts" choline chloride, sodium acetate, and acetylcholine iodide. This protection was accompanied by a loss of absorbance at 280 nm. This data supports the hypothesis that thermal inactivation of AChE occurs by conformational scrambling and that aromatic amino acid residue(s) are involved in this process.

Human serum butyrylcholinesterase (EC 3.1.1.8) loses 100% of its activity toward butyrylthiocholine in 60 min at pH 3.0. This deactivation is retarded by 1.37 M ammonium sulfate to a loss of 40% after 60 min at pH 3.0. Reneutralization experiments suggest that the mechanism for this acid inactivation does not exclusively involve hydrolysis of peptide bonds or protonation of the enzyme's active site. Studies with different anions and cations demonstrate that the order of their effectiveness as protective agents against acid inactivation closely follows the Hofmeister series. No relationship was found between catalytic activation or inhibition by salt and protection from acid inactivation. Ultraviolet difference studies at 288 nm with enzyme brought to pH 2.7 from pH 8.0 in the presence and absence of 1.37 M ammonium sulfate demonstrated no change in UV absorbance with ammonium sulfate present and approximately a 0.15 ODU rise in absorbance in the absence of ammonium sulfate. These results suggest that acidic pH conditions result in deactivating stereochemical changes in the active site of butyrylcholinesterase and that certain anions and cations, according to the Hofmeister series, are able to protect the enzyme from acid inactivation by stabilizing the active conformation of its active site.

Cuticle tissue homogenates (CTHs) from Callinectes sapidus premolt cuticle bound approximately 367% more Ca2+ ions than did those from the postmolt cuticle. The pH-stat assay which was used to compare in vitro CaCO3 nucleation times confirmed that the premolt CTHs had greater inhibitory activity than did the postmolt CTHs. This inhibitory activity was indicated by CaCO3 nucleation times in excess of control values. Premolt nucleation times exceeded those of postmolt samples by approximately 340%. A positive correlation was observed between Ca2+ binding and calcification inhibitory activity for both premolt and postmolt CTHs. Heat pretreatment of CTHs at 70 degrees C for a 24-hr period had no significant effect on their Ca2+ binding. However, this heat pretreatment decreased their calcification inhibitory activity. Pretreatment of CTHs with Ca2+ diminished their calcification inhibitory activity. These results are consistent with a mechanism for inhibition of biocalcification by these proteins which involves their initial reversible binding to nascent calcite nuclei growth steps and kinks, rather than their in vivo interaction with free Ca2+ ions in solution.

General chemistry courses designed for nursing students are becoming standard at academic institutions offering the Bachelor of Science in Nursing (BSN) degree. A good performance in chemistry, usually a grade of C or better, is essential for a student's acceptance into the institution's nursing school. While some of these nursing chemistry courses are not as difficult as the corresponding mainstream general chemistry courses offered, others maintain the same level of difficulty but only include general chemistry topics of particular relevance to nursing majors. Because of either differences in difficulty or content, most of these courses, including the one offered at our institution, the University of North Carolina at Wilmington (UNCW), cannot be applied toward a science major if a student decides to change majors after completing this course.It is widely accepted in both the chemical and nursing professional communities that general chemistry is an essential component of a nurse's education. There is disagreement, however, concerning whether nursing students have the ability to perform at the same level in general chemistry as mainstream general chemistry students. In this study we have compared the performances of students taking a general chemistry course for nursing majors to that of students taking a regular general chemistry course. The results presented in this paper characterize the chemical capabilities of the pre-nursing student population at UNCW. It is probable that other academic institutions that offer the BSN degree deal with student populations of similar composition. MethodsTo conduct this performance comparison we have used two general chemistry courses, Chemistry 101 and Chemistry 115, taught in the Chemistry Department at UNCW. These courses serve different student populations. Chemistry 101 is the first semester of general chemistry taken by all science majors. It satisfies the ACS certification requirements for a BS degree in chemistry.Chemistry 115, a one-semester general chemistry course designed for nursing majors, is usually taken the first semester of the freshman year. Before consideration for admission into the UNCW School of Nursing, a student must earn a grade of C or better in this course.Both Chemistry 101 and Chemistry 115 require precalculus as a prerequisite or corequisite. Both courses are available as basic studies science electives for any of UNCW's majors. However, most liberal arts majors that choose chemistry to fulfill their science elective take a separate chemistry course designed for them rather than Chemistry 101 or Chemistry 115. Topics covered in both Chemistry 101 and Chemistry 115 are listed in Table 1. Topics not common to both chemistry courses are listed in Table 2.A performance comparison was conducted in the Fall 1985 semester. Variables other than student population were minimized. There were three instructors for three sections of Chemistry 101, while the senior author, S. K. Burgess, was the instructor for one section of Chemistry 115. There were 146 Ch...