The TATA-binding protein from Saccharomyces cerevisiae oligomerizes in solution at micromolar concentrations to form tetramers and octamers

Equilibrium analytical ultracentrifugation has been used to determine the stoichiometry and energetics of the self-assembly of the TATA-binding protein of Saccharomyces cerevisiae at 30 degreesC, in buffers ranging in salt concentration from 60 mM KCl to 1 M KCl. The data are consistent with a sequential association model in which monomers are in equilibrium with tetramers and octamers at protein concentrations above 2.6 microM. Association is highly cooperative, with octamer formation favored by approximately 7 kcal/mol over tetramers. At high [KCl], the concentration of tetramers becomes negligible and the data are best described by a monomer-octamer reaction mechanism. The equilibrium association constants for both monomer <--> tetramer and tetramer <--> octamer reactions change with [KCl] in a biphasic manner, decreasing with increasing [KCl] from 60 mM to 300 mM, and increasing with increasing [KCl] from 300 mM to 1 M. At low [KCl], approximately 3 mole equivalents of ions are released at each association step, while at high [KCl], approximately 3 mole equivalents of ions are taken up at each association step. These results suggest that there is a salt concentration-dependent change in the assembly mechanism, and that the mechanistic switch takes place near 300 mM KCl. The possibility that this self-association reaction may play a role in the activity of the TATA-binding protein in vivo is discussed.     

Evaluation of the corrosion resistance of anodized aluminum 6061 using electrochemical impedance spectroscopy (EIS)

The corrosion resistance of anodized Al 6061 produced by two different anodizing and sealing processes was evaluated using electrochemical impedance spectroscopy (EIS). The scanning electron microscope (SEM) was employed to determine the surface structure and the thickness of the anodized layers. The EIS data revealed that there was very little change of the properties of the anodized layers for samples that were hard anodized in a mixed acid solution and sealed in hot water over a 365 day exposure period in a 3.5 wt% NaCl solution. The specific admittance A_s and the breakpoint frequency f_b remained constant with exposure time confirming that the hard anodizing process used in this study was very effective in providing excellent corrosion resistance of anodized Al 6061 over extended exposure periods. Some minor degradation of the protective properties of the anodized layers was observed for samples that were hard anodized in H₂SO₄ and exposed to the NaCl solution for 14 days.     

Virtual Human versus Human Administration of Photographic Lineups

One solution to mistaken identification by a crime's victims and eyewitnesses is to use a virtual officer to conduct identification procedures. Results from a study comparing a virtual officer with a live human investigator indicate that the virtual officer performs comparably to the human in terms of identification accuracy, emotional affect, and ease of use.     

The effect of stabilizing agents on the hydration rate of β-C2S

Small quantities (<2%) of various metal oxides are incorporated into the lattice of β-C₂S during the high temperature preparation. The effect which these stabilizers have on the hydration rate is examined. A model involving the charge/radius ratio of the metal ion is developed to explain altered hydration rates. This charge/ radius ratio model also proves useful in describing the crystal-chemical stabilization of β-C₂S. In addition, the solubility of Cr₂O₃ in β-C₂S is determined by a novel differential thermal analysis technique.     

Transistor input distortion and emitter degeneration

In the design of class A transistor amplifiers it is desirable to be able to predict and control the amount of distortion produced by the nonlinearity of the transistor input characteristic. This note presents an extension of a previously published method, to include the effects of emitter degeneration. The result provides a convenient means of determining the degenerations required to reduce the second-harmonic distortion to a given level.     

Antibody affinity maturation using bacterial surface display

A drug-resistant cell line (EAC/Dox) was developed by repeated exposure of Ehrlich ascites carcinoma cells to Doxorubicin (Dox) in vivo in male albino Swiss mice (6-8 weeks old). The weekly i.p. injections of Dox to mice (2 or 4 mg/kg/week for 4 months) gave rise to Dox-resistant cell line EAC/Dox, which displayed typical multidrug resistant (MDR) features of cross-resistance to a number of structurally and functionally unrelated drugs like doxorubicin, vinblastine and cisplatin. Moreover, the EAC/Dox cell line had lower drug accumulation than drug-sensitive (EAC/S) cells. Study of Western blots and immunofluorescence revealed that P-glycoprotein 170 kDa (P-gp) was absent in EAC/Dox cells. The drug resistance appeared to be due to the presence of a higher level of reduced glutathione (GSH) and glutathione S-transferase (GST) in EAC/Dox cells than in drug-sensitive (EAC/S) cells. The two structurally similar hydroxamic acid derivatives, i.e. oxalyl bis(N-phenyl)hydroxamic acid (X1) and succinyl bis(N-phenyl)hydroxamic acid (X2), having very low in vitro toxicity (IC50 value 250 microg/ ml), were investigated for their efficacy to reverse MDR. The compound X1 was able to reverse the effect of MDR and reduce GST in EAC/Dox cells. The compound X2 had no ability to reverse the effect of MDR. Further study on the mechanism of glutathione depletion and the resistance modifying property of X1 on other cell lines is warranted.     

Atherosclerosis: cell biology and lipoproteins

The theory of vibration-rotation interactions in polyatomic molecules using curvilinear internal coordinates for the vibrational degrees of freedom is extended to the situation where the initial molecular axis system is not the principal axis system of the equilibrium configuration. For this new situation, the transformation coefficient rhoit is derived as well as the vibrational coefficients (G-1tt')0. This new transformation may not be useful nor necessary when all of the internal motions are of small amplitude. However, in the case of vibration-rotation-internal rotation interactions, the new transformation is helpful when the internal rotor is a symmetric top and necessary when the internal rotor is an asymmetric top. Copyright 1998 Academic Press. Copyright 1998Academic Press     

Apolipoprotein E-deficient mice have impaired innate immune responses to Listeria monocytogenes in vivo

Apolipoprotein E (apoE) influences both innate and acquired immunity in cultured cells. To determine whether apoE affects the immune system in vivo, Listeria monocytogenes (LM) was administered intraperitoneally (10(4) c.f.u.) to congenic C57BL/6 apoE-/- and +/+ mice (n = 12 in each group). Survival was assessed daily for 5 days. Deficiency of apoE significantly increased death by day 5 (P = 0.03). The majority of deaths occurred at day 4. Extent of infection after LM administration was assessed at day 3 by determining colony counts in hepatic and splenic extracts. ApoE+/+ mice had very low colony counts in both spleen and liver [mean +/- SE: 2.0 +/- 0.5 and 0.7 +/- 0.2 (x 10(4)), respectively, n = 8 in each group]; while apoE-/- mice had significantly increased counts in both spleen and liver [64 +/- 51 and 98 +/- 93 (x 10(4)), P = 0.05 and 0.03]. Serum concentrations of TNF-alpha were significantly increased in apoE-/- mice at day 3 compared to apoE+/+ mice (127 +/- 43 pg/ml versus 20 +/- 17, P = 0.003). LM induced more hepatic damage in apoE-/- mice compared to apoE+/+ mice as judged by increased serum concentrations of alanine aminotransferase at day 1 (apoE-/- 301 +/- 45 U/ml, apoE+/+ 101 +/- 9 U/ml, P = 0.01). The increased proliferation and mortality from LM in apoE-/- mice occurred prior to the initiation of acquired immune responses. Therefore, apoE-deficient mice have an impaired innate response to infection by LM.