Mechanistic study of beta-substituent effects on the mechanism of ketone reduction by SmI(2)

The rate constants for the reduction of 2-butanone, methylacetoacetate, N, N-dimethylacetoacetamide, and a series of 4'- and 2'-substituted acetophenone derivatives by SmI(2) were determined in dry THF using stopped-flow absorption decay experiments. Activation parameters for the electron-transfer processes in each series of compounds were determined by a temperature-dependence study over a range of 30 to 50 degrees C. Two types of reaction pathways are possible for these electron-transfer processes. One proceeds through coordination (Scheme 1) while the other involves chelation (Scheme 2). The results described herein unequivocally show that both coordination and chelation provide highly ordered transition states for the electron-transfer process but the presence of a chelation pathway dramatically increases the rate of the reduction of these substrates by SmI(2). The ability of various functional groups to promote a chelated reaction pathway plays a crucial role in determining the rate of the reaction. Among the 2'-substituted acetophenone series, the presence of a fluoro, amino, or methoxy substituent enhances the rate of reduction compared to the 4'-analogues. In particular, the presence of a 2'-fluoro substituent on acetophenone provides a highly ordered transition state and considerably enhances the rate of ketone reduction.     

Detection of heterogeneity of apoptotic fragments of poly (ADP-ribose) polymerase in MDA-MB-468 breast cancer cells: two-dimensional gel analysis

Caspace-mediated proteolysis of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) (EC 2.4, 2.30) is a biochemical marker of cell death in response to various apoptotic stimuli. Anti-PARP antibodies identifying the 89 kDa polypeptide from the C-terminus as well as the 113 kDa native enzyme are often used to demonstrate evidence of apoptosis-associated, interleukin converting enzyme (ICE)-mediated limited cleavage. Recent evidence points to redundancy of caspases, heterogeneity of their cleavage sites, and a possibility of generating distinct context-specific, and cell-specific PARP fragments. In the present study, we employed antibodies directed to multiple sites in PARP and probed two-dimensionally resolved proteins of the estrogen receptor negative MDA-MB-468 breast tumor cells, induced to undergo apoptosis by ionizing radiation (IR). Our results revealed that the 24 kDa apoptotic fragment of PARP, from the N-terminus, consists of at least three isoforms, located at a p/more basic than the full length enzyme. We also report a hitherto unrecognized feature of an anti-PARP antiserum, VIC-5, detecting both the 89 kDa and the 24 kDa caspase-generated fragments of PARP. Thus, application of two-dimensional electrophoresis combined with antisera directed to multiple sites would be valuable in distinguishing PARP cleavage site- and inhibitor specificities of proteases during apoptosis.     

Switching surfaces inN-person differential games

Switching surfaces inN-person differential games are essentially similar to those encountered in optimal control and two-person, zero-sum differential games. The differences between the Nash noncooperative solution and the saddle-point solution are reflected in the dispersal surfaces. These are discussed through classification and construction procedures for switching surfaces. A simple example of a two-person, nonzero-sum game is considered. A complete solution of this game will be presented in a companion paper (Ref. 1).     

Polynomial basis for the irreducible representations of U6 in the chain U6 ⊃ R6

Explicit polynomial basis for the Irreducible Representation (IR) (K₁, K₂, K₃) of U₆ containing an IR (λ₁, λ₂, λ₃) of R₆ is obtained. These polynomials are useful in calculating the nuclear energy levels in the2s? 1d shell.     

Measurement of multiplet intensities and noble gas-broadened line widths in the V3-fundamental of methane

Integrated intensity data at 300°K for J-multiplets between P(11)and R(11) in the _{V3-fundamental of ¹²CH4} are presented, along with the intensity of the entire Q-branch, which also encompasses the Q-branch of the _{V3-fundamental of ¹³CH4}. These data, together with theoretical estimates for the intensities of J-multiplets of J > 11, sum up to a value of S_band= 284±14cm^?2atm^?1 at 300°K. This results is in excellent agreement with most of the previously published values for this parameter. Within experimental error, the intensities of the J-multiplets in the _{V3-fundamental do not seem to exhibit the strong anamolies that were characteristic of lines in the 2V3}-band.Line widths have been measured at 100°K, 130°K, 190°K, 250°K, and 300°K for R(0), R(1), and R(2) broadened by He, Ne and Ar. The temperature dependence of the line width is discussed for the three cases of broadening. In neon broadening at 300°K, the ‘effective mean line widths’ for multiplets R(3) through R(11) have also been obtained experimentally; their J-dependence is interpreted using Gordon's theory of line shapes in multiplet spectra.     

Kinetics of thermal decomposition of intermediate hydrates and basic salts of iron(II) sulphate heptahydrate

The kinetics of thermal decomposition of iron(II) sulphate hexa- to monohydrates, as well as the hydroxy- and oxysulphates of iron(III), are presented and discussed. The results confirm that the final intermediate that decomposes to iron(III) oxide and sulphur trioxide during the thermal decomposition of any hydrate of iron(II) sulphate is the oxysulphate, Fe₂O(SO₄)₂.

---

Zusammenfassung Die Kinetik der thermischen Zersetzung von Eisen(II)-sulfat-Hexahydrat zum Monohydrat und von Hydroxy- und Oxysulfaten von Eisen(III) ist angegeben und wird diskutiert. Die Ergebnisse bestätigen, daß das letzte, sich zu Eisen(III)-oxid und Schwefeltrioxid zersetzende Zwischenprodukt bei der thermischen Zersetzung aller Hydrate von Eisen(II)-sulfat das Oxysulfat Fe₂O(SO₄)₂ ist.

---

( - ) , . , - Fe₂O(SO₄)₂, .

---

---

The author is grateful to Prof. P. K. Jena, Director, for his kind permission to publish the results.