Attachment and adolescent psychosocial functioning

To explore the meaning and function of attachment organization during adolescence, its relation to multiple domains of psychosocial functioning was examined in a sample of 131 moderately at-risk adolescents. Attachment organization was assessed using the Adult Attachment Interview; multiple measures of functioning were obtained from parents, adolescents, and their peers. Security displayed in adolescents' organization of discourse about attachment experiences was related to competence with peers (as reported by peers), lower levels of internalizing behaviors (as reported by adolescents), and lower levels of deviant behavior (as reported by peers and by mothers). Preoccupation with attachment experiences, seen in angry or diffuse and unfocused discussion of attachment experiences, was linked to higher levels of both internalizing and deviant behaviors. These relations generally remained even when other attachment-related constructs that had been previously related to adolescent functioning were covaried in analysis. Results are interpreted as suggesting an important role for attachment organization in a wide array of aspects of adolescent psychosocial development.

A conformational change of the photoactive bacteriopheophytin in reaction centers from Rhodobacter sphaeroides

It is demonstrated by ENDOR and Special TRIPLE spectroscopy that two distinct radical anion states of the intermediate electron acceptor (I), a bacteriopheophytin, can be freeze-trapped in isolated photosynthetic reaction centers of Rhodobacter sphaeroides. The formation of these states depends on the illumination time prior to freezing and the temperature. The first state, I1.-, is metastable and relaxes irreversibly at T approximately 160 K to the second state, I2.-. Experiments on quinone depleted as well as mutant reaction centers help to exclude the possibility that other cofactors besides the bacteriopheophytin in the A-branch, PhiA, are reduced during the trapping procedure. In particular, two mutants are investigated, in which the hydrogen bonds to PhiA that exist in the wild type are removed. These mutants are EL(L104), in which Glu at position L104 near the 13(1)-keto group of PhiA is replaced by Leu, and WF(L100), in which Trp at position L100 near the 13(2)-methyl ester of PhiA is replaced by Phe. Both mutations have characteristic effects on both I.- states. In addition, the replacement of Thr at position M133 near the 13(1)-keto group of the inactive bacteriopheophytin and of Gly at position M203 near the 13(1)-keto group of the accessory bacteriochlorophyll in the A-branch by Asp causes no changes of the electronic structure of I.-. The two I.- states are interpreted in terms of a reorientation of the 3-acetyl group of PhiA after reduction. Possible implications for the initial charge separation process are discussed.

Advances in development of medications for alcoholism treatment

Over the past decade, research on medications to treat alcohol problem has flourished. Naltrexone and acamprosate are tangible fruits of such endeavors and each has now earned approval in a large number of countries. Recent studies on naltrexone indicate that patient compliance is important if full benefits are to be achieved. Several laboratory studies with human subjects are beginning to elucidate the mechanisms underlying efficacy of naltrexone, as well as explaining variability of response among subpopulations of drinkers. In addition to these two agents, recent investigations have also demonstrated that the antidepressants desipramine, imipramine, and fluoxetine reduce mood-related symptoms and, to some extent, drinking itself in alcoholics who are depressed. Research to date suggests that opioid antagonists and selective serotonin reuptake inhibitors are more effective in reducing alcohol intake when used in combination. Clinical issues, methodology, and directions for future research are also reviewed in this article. In particular, issues addressed include alternative dosage regimens, necessary duration of treatment, employment of medications in combination, integration of pharmacologic agents with behavioral interventions, enhancement of patient compliance, and concurrent treatment of psychiatric comorbidity.

Effects of hydrogen bonds on the redox potential and electronic structure of the bacterial primary electron donor

The primary donor, P, of photosynthetic bacterial reaction centers (RCs) is a dimer of excitonically interacting bacteriochlorophyll (BChl) molecules. The two constituents are named PL and PM to designate their close association with the L- and M-subunits, respectively, of the RC protein. A series of site-directed mutants of RCs from Rhodobacter sphaeroides has been constructed in order to model the effects of hydrogen bonding on the redox midpoint potential and electronic structure of P. The leucine residue at position M160 was genetically replaced with eight other amino acid residues capable of donating a hydrogen bond to the C9 keto carbonyl group of the PM BChl a molecule of P. Fourier transform (FT) (pre)resonance Raman spectroscopy with 1064 nm excitation was used to (i) determine the formation and strengths of hydrogen bonds on this latter keto carbonyl group in the reduced, neutral state (PO), and (ii) determine the degree of localization of the positive charge on one of the two constituent BChl molecules of P in its oxidized, radical cation state (P*+). A correlation was observed between the strength of the hydrogen bond and the increase in PO/P*+ redox midpoint potential. This correlation is less pronounced than that observed for another series of RC mutants where hydrogen bonds to the four pi-conjugated carbonyl groups of P were broken or formed uniquely involving histidinyl residues [Mattioli, T. A., Lin, X., Allen, J. P. and Williams, J. C. (1995) Biochemistry 34, 6142-6152], indicating that histidinyl residues are more effective in raising the PO/P*+ redox midpoint potential via hydrogen bond formation than are other hydrogen bond-forming residues. In addition, an increase in positive charge localization is correlated with the strength of the hydrogen bond and with the PO/P*+ redox midpoint potential. This latter correlation was analyzed using an asymmetric bacteriochlorophyll dimer model based on Hückel-type molecular orbitals in order to obtain estimates of certain energetic parameters of the primary donor. Based on this model, the correlation is extrapolated to the case of complete localization of the positive charge on PL and gives a predicted value for the P/P+ redox midpoint potential similar to that experimentally determined for the Rb. sphaeroides HL(M202) heterodimer. The model yields parameters for the highest occupied molecular orbital energies of the two BChl a constituents of P which are typical for the oxidation potential of isolated BChl a in vitro, suggesting that the protein, as compared to many solvents, does not impart atypical redox properties to the BChl a constituents of P.

Effects of temperature and deltaGo on electron transfer from cytochrome c2 to the photosynthetic reaction center of the purple bacterium Rhodobacter sphaeroides

The kinetics of electron transfer from cytochrome c2 to the primary donor (P) of the reaction center from the photosynthetic purple bacterium Rhodobacter sphaeroides have been investigated by time-resolved absorption spectroscopy. Rereduction of P+ induced by a laser pulse has been measured at temperatures from 300 K to 220 K in a series of specifically mutated reaction centers characterized by altered midpoint redox potentials of P+/P varying from 410 mV to 765 mV (as compared to 505 mV for wild type). Rate constants for first-order electron donation within preformed reaction center-cytochrome c2 complexes and for the bimolecular oxidation of free cytochrome c2 have been obtained by multiexponential deconvolution of the kinetics. At all temperatures the rate of the fastest intracomplex electron transfer increases by more than two orders of magnitude as the driving force -deltaGo is varied over a range of 350 meV. The temperature and deltaGo dependences of the rate constant fit the Marcus equation well. Global analysis yields a reorganization energy lambda = 0.96 +/- 0.07 eV and a set of electronic matrix elements, specific for each mutant, ranging from 1.2 10(-4) eV to 2.5 10(-4) eV. Analysis in terms of the Jortner equation indicates that the best fit is obtained in the classical limit and restricts the range of coupled vibrational modes to frequencies lower than approximately 200 cm(-1). An additional slower kinetic component of P+ reduction, attributed to electron transfer from cyt c2 docked in a nonoptimal configuration of the complex, displays a Marcus type dependence of the rate constant upon deltaGo, characterized by a similar value of lambda (0.8 +/- 0.1 eV) and by an average electronic matrix element smaller by more than one order of magnitude. In all of the mutants, as the temperature is decreased below 260 K, both intracomplex reactions are abruptly inhibited, their rate being negligible at 220 K. The free energy dependence of the second-order rate constant for oxidation of cyt c2 in solution suggests that the collisional reaction is partially diffusion controlled, reaching the diffusion limit at exothermicities between 150 and 250 meV over the temperature range investigated.

Pharmacologic treatment of alcoholics with collateral depression: issues and future directions

Patients in treatment for alcoholism often suffer collateral depressive disorders. Fortunately, recent advances in medications development may significantly improve outcome for this population, but there remain several concerns about the clinical use of pharmacologic agents in these cases. These concerns are discussed, as are research findings that bear on them. Directions for future research are also identified.

Screening for alcohol problems in the military: recommended tests

This article suggests two new techniques for identifying alcohol problems in a military setting. The Alcohol Use Disorders Identification Test is a well validated self-report procedure and requires approximately 2 minutes for administration. Measurement of carbohydrate-deficient transferrin provides a useful biochemical index of recent heavy alcohol consumption. Employment of these tests could improve selection of individuals seeking entry to the military, aid recognition of current personnel in need of treatment, and assist in evaluating progress of patients in treatment.

Relationship between the oxidation potential and electron spin density of the primary electron donor in reaction centers from Rhodobacter sphaeroides

The primary electron donor in bacterial reaction centers is a dimer of bacteriochlorophyll a molecules, labeled L or M based on their proximity to the symmetry-related protein subunits. The electronic structure of the bacteriochlorophyll dimer was probed by introducing small systematic variations in the bacteriochlorophyll-protein interactions by a series of site-directed mutations that replaced residue Leu M160 with histidine, tyrosine, glutamic acid, glutamine, aspartic acid, asparagine, lysine, and serine. The midpoint potentials for oxidation of the dimer in the mutants showed an almost continuous increase up to approximately 60 mV compared with wild type. The spin density distribution of the unpaired electron in the cation radical state of the dimer was determined by electron-nuclear-nuclear triple resonance spectroscopy in solution. The ratio of the spin density on the L side of the dimer to the M side varied from approximately 2:1 to approximately 5:1 in the mutants compared with approximately 2:1 for wild type. The correlation between the midpoint potential and spin density distribution was described using a simple molecular orbital model, in which the major effect of the mutations is assumed to be a change in the energy of the M half of the dimer, providing estimates for the coupling and energy levels of the orbitals in the dimer. These results demonstrate that the midpoint potential can be fine-tuned by electrostatic interactions with amino acids near the dimer and show that the properties of the electronic structure of a donor or acceptor in a protein complex can be directly related to functional properties such as the oxidation-reduction midpoint potential.

Crystal structure of the bacteriochlorophyll a protein from Chlorobium tepidum

The bacteriochlorophyll (BChl) a protein from Chlorobium tepidum, which participates in energy transfer in green photosynthetic bacteria, has been crystallized using the sitting drop method of vapor diffusion. X-ray diffraction data collected from these crystals indicate that the crystals belong to the cubic space group P4132 with cell dimensions of a=b=c=169.5 A. A native X-ray diffraction data set has been collected to a resolution of 2.2 A. The initial solution was determined by using the molecular replacement method using the structure of the previously solved BChl a protein from Prosthecochloris aestuarii. A unique rotation and translation solution was obtained for two monomers in the asymmetric unit giving a pseudo-body centered packing. After rebuilding and refinement the model yields an R factor of 19.0%, a free R-factor of 28.3%, and good geometry with root-mean-square deviations of 0.013 A and 2.1 degrees for the bond lengths and angles, respectively. The structure of the BChl a protein from C. tepidum consists of three identical subunits related by a 3-fold axis of crystallographic symmetry. In each subunit the polypeptide backbone forms large beta-sheets and encloses a central core of seven BChl a molecules. The distances between neighboring bacteriochlorin systems within a subunit range between 4 A to 11 A and that between two bacteriochlorins from different subunits is more than 20 A. The overall structure is comparable with that of P. aestuarii but significant differences are observed for the individual bacteriochlorophyll structures. The surface of the trimer has a hydrophobic region that is modeled as the complex being a peripheral membrane protein partially embedded in the membrane. A general model is presented for the membrane organization with two of the bacteriochlorophyll structures in the membrane and transferring energy to the reaction center complex. In this model these two bacteriochlorophyll structures serve a similar role to the cofactors of integral membrane light-harvesting complexes although the protein structure surrounding the cofactors is significantly different for the BChl a protein compared with the integral membrane complexes.

A review of research on the Alcohol Use Disorders Identification Test (AUDIT)

Research on the core version of the Alcohol Use Disorders Identification Test (AUDIT) is reviewed. Sensitivities and specificities of the AUDIT or criteria of current hazardous use and, to a slightly lesser extent, lifetime alcohol dependence are high. In general, AUDIT scores are at least moderately related to other self-report alcohol screening tests. Several studies also show them as correlated with biochemical measures of drinking. Results of the AUDIT have also been associated with more distal indicators of problematic drinking. Indices of internal consistency, including Cronbach's alpha and item-total correlations, are generally in the 0.80's. Future directions for research on the AUDIT are suggested.

Electrostatic influence of QA reduction on the IR vibrational mode of the 10a-ester C==O of HA demonstrated by mutations at residues Glu L104 and Trp L100 in reaction centers from Rhodobacter sphaeroides

The light-induced QA-/QA FTIR difference spectrum of the photoreduction of the primary quinone (QA) in reaction centers (RCs) from Rhodobacter sphaeroides exhibits a set of complex differential bands between 1750 and 1715 cm(-1). Several of these features correspond in frequency to bands that bleach in the HA-/HA FTIR difference spectra of the photoreduction of the bacteriopheophytin electron acceptor (HA). Since the 10a-ester C==O from HA and the side chains of protonated carboxylic acids would be expected to contribute in this spectral region, mutations were designed at Trp L100 and Glu L104, which have been proposed to form hydrogen bonds to the 10a-ester and the 9-keto carbonyls on ring V of HA, respectively. The QA/-/QA spectra measured in IH2O and 2H2O of RCs from wild type (WT) were compared to those of RCs with the mutation Trp to Phe at L100 [WF(L100)], Glu to Leu at L104 [EL(L104)], or both mutations [EL(L104)/WF(L100)]. The spectra of the mutants in the 1800-1400 cm(-1) frequency range exhibit only limited perturbations compared to those of WT, indicating the absence of significant structural changes due to the mutations. Part of a differential signal centered around 1732 cm(-1) in the spectrum of WT RCs is downshifted by approximately 7 cm(-1) in EL(L104), while it is upshifted by approximately 11 cm(-1) in WF(L100). This upshift of the differential signal is assigned to the frequency change of the 10a-ester C==O of HA induced by the rupture of the hydrogen bond with Trp L100. The 1H2O-minus-2H2O double-difference spectrum of WT RCs exhibits a characteristic differential signal positive at 1730 cm-1 and negative at 1724 cm-1 that is absent in the corresponding spectra of EL(L104) and of the double mutant, implicating Glu L104 in the QA-/QA spectral changes. This differential signal is strongly modified in frequency and amplitude in the 1H2O-minus-2H2O spectrum of WF(L100), indicating that it does not correspond to a direct response of the C==O mode of the Glu L104 side chain upon QA reduction. Instead, perturbation of the hydrogen bond of the 9-keto C==O with Glu L104 is proposed to induce a change of electron density on ring V of HA, thereby altering the frequency of the 10a-ester C==O that is in partial conjugation with ring V. The loss of the hydrogen bond to the 9-keto C==O of HA due to the Glu L104 to Leu mutation or the alteration of the strength of the hydrogen bond by 1H/2H exchange on Glu L104 appears to produce such effects. Thus, the QA-/QA spectra above 1700 cm-1 are dominated by contributions from the 10a-ester C==O of HA, with most of the differential signals assigned to a small frequency downshift of the 10a-ester C==O of HA in response to QA reduction. The complexity of the signals implies a structural heterogeneity of the conformation and hydrogen bonding of the 10a-ester C==O of HA, which may be related to the functional heterogeneity observed in electron transfer kinetics. The present FTIR results show that the reduction of QA can induce a pronounced electrostatic effect on molecular vibrations of chemical groups located about 10 A away from QA. They also demonstrate that, within experimental limits, the proton uptake observed at pH 7 upon QA photoreduction [McPherson, P. H., Okamura, M. Y., & Feher, G. (1988) Biochim. Biophys. Acta 934, 348-368] involves none of the exchangeable carboxylic groups of the RC.

Proposed recommendations for research on biochemical markers for problematic drinking

Biochemical markers can serve as valuable tools in screening for problematic drinking, determining whether a health problem is likely alcohol related, and monitoring alcoholics for relapse during and after treatment. Furthermore, biochemical markers can assist in forensic investigations; in identification of public health, safety, and transportation workers who may drink excessively and who, as a result, may put others at risk; in evaluation of efficacy of treatments for alcohol abuse; and in recognition of early phase alcohol-related tissue damage. Within all of these contexts, a biochemical marker or set of markers may corroborate verbal reports or may provide valuable independent information on alcohol use when an individual is unable or unwilling to offer valid data about alcohol consumption.

Attachment theory as a framework for understanding sequelae of severe adolescent psychopathology: an 11-year follow-up study

This study examined long-term sequelae of severe adolescent psychopathology from the perspective of adult attachment theory. The study compared 66 upper-middle-class adolescents who were psychiatrically hospitalized at age 14 for problems other than thought or organic disorders, to 76 sociodemographically similar high school students. When reinterviewed at age 25, virtually all of the previously hospitalized adolescents displayed insecure attachment organizations, in contrast to a more typical mixture of security and insecurity in the former high school sample. Lack of resolution of previous trauma with attachment figures accounted for much of this insecurity. Insecurity in adult attachment organization at age 25 was also linked to self-reported criminal behavior and use of hard drugs in young adulthood. These findings are discussed as reflecting a substantial and enduring connection between attachment organization and severe adolescent psychopathology and a possible role of attachment organization in mediating some of the long-term sequelae of such psychopathology.

Health behavior correlates of hazardous drinking by Army personnel

The current investigation determined that military personnel who drink heavily differ from those who drink moderately in the practice of nine behaviors often associated with unhealthy lifestyle. In particular, excessive drinkers were found to smoke more, drive dangerously more frequently, and consume saturated fats more often. The project further found that the relationship of excessive drinking to these activities is mediated by age, marital status, and race, although not by gender or rank. Implications of the findings for prevention and treatment are suggested.

Assessment of invasive growth pattern and lymphocytic infiltration in colorectal cancer

A total of 122 specimens of colorectal cancer were re-assessed in relation to the reporting of invasive growth pattern (expanding vs. infiltrating) and presence or absence of peritumoral lymphocytic infiltrate as used in the Jass prognostic classification. Jass agreed with 69% of cases reported as infiltrating and 90% of reported as expanding. This parameter was distributed similarly amongst Dukes B and C cases in the original assessment (P = 0.27), whereas in the reviewed data infiltrating cases were more likely to be staged as Dukes C (P = 0.04). Jass agreed with 44% of lymphocyte present and 94% of lymphocyte absent assessments. The original lymphocyte assessments showed no significant differences in distribution between Dukes A and B cases (P = 0.12) or B and C cases (P = 0.75), whereas the reviewed data showed significant differences for A vs. B (P = 0.015) and B vs. C cases (P = 0.0025). Criteria for assessment were circulated to eight observers who revisited 20 of the cases in which there was disagreement. Consensus agreement with Jass was achieved in nine of 10 cases for invasive growth pattern and seven of 10 cases for lymphocyte infiltration (with two being evenly split). Most observers showed at least fair levels of agreement with Jass and some achieved excellent levels of agreement. This study indicates that assessment of criteria used in the Jass prognostic system for colorectal cancer is less than optimal in routine practice, but is improved through the provision of simple guidelines.

Effects of hydrogen bonding to a bacteriochlorophyll-bacteriopheophytin dimer in reaction centers from Rhodobacter sphaeroides

The properties of the primary electron donor in reaction centers from Rhodobacter sphaeroides have been investigated in mutants containing a bacteriochlorophyll (BChl)--bacteriopheophytin (BPhe) dimer with and without hydrogen bonds to the conjugated carbonyl groups. The heterodimer mutation His M202 to Leu was combined with each of the following mutations: His L168 to Phe, which should remove an existing hydrogen bond to the BChl molecule; Leu L131 to His, which should add a hydrogen bond to the BChl molecule; and Leu M160 to His and Phe M197 to His, each of which should add a hydrogen bond to the BPhe molecule [Rautter, J., Lendzian, F., Schulz, C., Fetsch, A., Kuhn M., Lin, X., Williams, J. C., Allen J. P., & Lubitz, W. (1995) Biochemistry 34, 8130-8143]. Pigment extractions and Fourier transform Raman spectra confirm that all of the mutants contain a heterodimer. The bands in the resonance Raman spectra arising from the BPhe molecule, which is selectively enhanced, exhibit the shifts expected for the addition of a hydrogen bond to the 9-keto and 2-acetyl carbonyl groups. The oxidation--reduction midpoint potential of the donor is increased by approximately 85 mV by the addition of a hydrogen bond to the BChl molecule but is only increased by approximately 15 mV by the addition of a hydrogen bond to the BPhe molecule. An increase in the rate of charge recombination from the primary quinone is correlated with an increase in the midpoint potential. The yield of electron transfer to the primary quinone is 5-fold reduced for the mutants with a hydrogen bond to the BPhe molecule. Room- and low-temperature optical absorption spectra show small differences from the features that are typical for the heterodimer, except that a large increase in absorption is observed around 860-900 nm for the donor Qy band in the mutant that adds a hydrogen bond to the BChl molecule. The changes in the optical spectra and the yield of electron transfer are consistent with a model in which the addition of a hydrogen bond to the BChl molecule increases the energy of an internal charge transfer state while the addition to the BPhe molecule stabilizes this state. The results show that the properties of the heterodimer are different depending on which side is hydrogen-bonded and suggest that the hydrogen bonds alter the energy of the internal charge transfer state in a well-defined manner.

Energy trapping and detrapping by wild type and mutant reaction centers of purple non-sulfur bacteria

Time-correlated single photon counting was used to study energy trapping and detrapping kinetics at 295 K in Rhodobacter sphaeroides chromatophore membranes containing mutant reaction centers. The mutant reaction centers were expressed in a background strain of Rb. sphaeroides which contained only B880 antenna complexes and no B800-850 antenna complexes. The excited state decay times in the isolated reaction centers from these strains were previously shown to vary by roughly 15-fold, from 3.4 to 52 ps, due to differences in the charge separation rates in the different mutants (Allen and Williams (1995) J Bioenerg Biomembr 27: 275-283). In this study, measurements were also performed on wild type Rhodospirillum rubrum and Rb. sphaeroides B880 antenna-only mutant chromatophores for comparison. The emission kinetics in membranes containing mutant reaction centers was complex. The experimental data were analyzed in terms of a kinetic model that involved fast excitation migration between antenna complexes followed by reversible energy transfer to the reaction center and charge separation. Three emission time constants were identified by fitting the data to a sum of exponential decay components. They were assigned to trapping/quenching of antenna excitations by the reaction center, recombination of the P(+)H(-) charge-separated state of the reaction center reforming an emitting state, and emission from uncoupled antenna pigment-protein complexes. The first varied from 60 to 160 ps, depending on the reaction center mutation; the second was 200-300 ps, and the third was about 700 ps. The observed weak linear dependence of the trapping time on the primary charge separation time, together with the known sub-picosecond exciton migration time within the antenna, supports the concept that it is energy transfer from the antenna to the reaction center, rather than charge separation, that limits the overall energy trapping time in wild type chromatophores. The component due to charge recombination reforming the excited state is minor in wild type membranes, but increases substantially in mutants due to the decreasing free energy gap between the states P(*) and P(+)H(-).

Attachment theory as a framework for understanding sequelae of severe adolescent psychopathology: an 11-year follow-up study

This study examined long-term sequelae of severe adolescent psychopathology from the perspective of adult attachment theory. The study compared 66 upper-middle-class adolescents who were psychiatrically hospitalized at age 14 for problems other than thought or organic disorders, to 76 sociodemographically similar high school students. When reinterviewed at age 25, virtually all of the previously hospitalized adolescents displayed insecure attachment organizations, in contrast to a more typical mixture of security and insecurity in the former high school sample. Lack of resolution of previous trauma with attachment figures accounted for much of this insecurity. Insecurity in adult attachment organization at age 25 was also linked to self-reported criminal behavior and use of hard drugs in young adulthood. These findings are discussed as reflecting a substantial and enduring connection between attachment organization and severe adolescent psychopathology and a possible role of attachment organization in mediating some of the long-term sequelae of such psychopathology.

Temperature dependence of the reorganization energy for charge recombination in the reaction center from Rhodobacter sphaeroides

The rate of charge recombination from the primary quinone to the bacteriochlorophyll dimer of the reaction center from the photosynthetic purple bacterium Rhodobacter sphaeroides has been investigated using time-resolved optical spectroscopy. Measurements were performed at temperatures from 293 to 10 K on reaction centers that have specific mutations that result in a range of 425-780 meV for the free energy difference of charge recombination compared to 520 meV for wild type [Lin, X., Murchison, H. A., Nagarajan, V., Parson, W. W., Allen, J. P., & Williams, J.C. (1994) Proc.Natl.Acad.Sci.U.S.A. 91, 10265-10269]. In all cases, the rate increased as the temperature decreased, although the details of the dependence were different for each mutant. The observed dependence of the rate upon temperature is modeled as arising principally from a several hundred meV change in reorganization energy. The relationships among the rate, temperature, and free energy differences can be well fit by a Marcus surface using two modes centered near 150 and 1600 cm(-1)with a total reorganization energy that decreases from 930 to 650 meV as the temperature decreases from 293 to 10 K. In the inverted region, where the driving force is greater than the reorganization energy, the rate is found to be approximately independent of the free energy difference. This is modeled as due to the additional coupling of high frequency modes to the reaction. An alternative model is also considered in which a 140 meV increase in the reorganization energy is matched by a 140 meV increase in the free energy difference as the temperature decreases. The possible role of solvent dipoles in determining this temperature dependence of the reorganization energy and the implications for other electron transfer reactions are discussed.

Contrasting self-report screens for alcohol problems: a review

Current trends in conceptions of alcohol problems and provision of health care put increased emphasis on identifying individuals whose alcohol use and problems cover a range of severity. The purpose of this study is to begin to provide information on the relative utility of self-report measures designed to identify (screen for) individuals with alcohol problems. To achieve this goal, the empirical literature on contrasts of self-report screening measures was reviewed, and 13 relevant studies across diverse settings and subject populations were identified. The review showed that the CAGE, the Michigan Alcoholism Screening Test (MAST), and the short MAST (sMAST) have been the most widely studied self-report instruments to screen for alcohol problems. Direct comparisons show the MAST to be more sensitive than the CAGE, but with elderly patients the CAGE may perform better than the MAST. Furthermore, available data suggest that the CAGE and the sMAST perform comparably. Finally, the CAGE, MAST, and sMAST all perform best when predicting criteria most similar to those the instruments were designed to reflect. The study concludes with a discussion of priorities for research on screening instruments.

Gamma-glutamyltranspeptidase and carbohydrate deficient transferrin: alternative measures of excessive alcohol consumption

Both gamma-glutamyltranspeptidase and carbohydrate-deficient transferrin have been extensively researched as biological markers of heavy alcohol consumption. The current study briefly describes each test, identifies subject variables that influence their relative sensitivities and specificities, and examines issues surrounding use of the two markers in combination. In addition, this study suggests five design features that should characterize projects evaluating the validity of biochemical markers.