Prevalence and Quantification of the Effects of Sexual Harassment Victimization of School-Aged Adolescents

BACKGROUND/AIM

Sexual harassment has become a serious social and public health problem in adolescents, causing adverse effects on mental health. Nevertheless, some behaviours arise that, due to their characteristics, might be misinterpreted as sexual harassment. A field study using a survey with non-probabilistic accidental sampling was designed in order to estimate the prevalence of sexual harassment victimization in the Spanish adolescent population as well as to quantify the harms.

METHOD

A total of 1028 Spanish adolescents, 54.3% females and 45.7% males aged 13-17 years (M = 15.21, SD = 1.03), responded to a diagnostic measure of sexual harassment victimization and an inventory measure of internalizing and externalizing mental health problems (MHPs).

RESULTS

The results showed a significant prevalence of diagnosed sexual harassment victimization of school-aged adolescents, 24.1%, 95% CI [0.215, 0.267], with adverse effects on internalizing and externalizing MHPs. As for the internalizing MHPs, the results exhibited moderate adverse effects on depression, anxiety, somatic burns, posttraumatic symptoms, and obsessive-compulsive symptoms, as well as mild adverse effects on social anxiety. Regarding externalizing MHPs, the results revealed moderate adverse effects on hyperactivity-impulsivity, anger control, and antisocial behaviour, as well as mild adverse effects on attention problems, aggression, and defiant behaviour. In addition, it was confirmed that sexual harassment victimization affects adolescent females to a greater extent, with the effect being significantly greater in internalizing than in externalizing MHPs.

CONCLUSIONS

The results obtained are discussed and future lines of research and intervention are proposed to promote the implementation of prevention and intervention programs that address this phenomenon and, in turn, improve the physical, psychological, and social well-being of adolescents.

Implanting rich autobiographical false memories: Meta-analysis for forensic practice and judicial judgment making

Objective

The implanting of rich autobiographical false memories is crucial for judicial decision-making, and the forensic evaluation of a testimony. In order to assess this issue, a meta-analytical review of the probability of implanting rich autobiographical false memories was performed.

Method

A total of 30 primary studies analysing the probability of implanting rich autobiographical false memories were retrieved. Random-effects meta-analyses correcting the effect size for sampling error were performed.

Results

The results revealed a significant, positive, generalizable (the lower limit for the 80% credibility value was d = 1.13), and more than large mean effect size (d = 1.43[1.33, 1.53]) for the implanting of false memory. The moderating effects of stimulus type showed that the effect of the probability of implanted false memory was significantly higher in experienced events (d = 2.03[1.63, 2.43]) than in false narratives (d = 1.35[1.23, 1.47]), and in doctored photographs (d = 1.29[1.06, 1.52]). A similar effect for memory implantation was observed in both the underage (d = 1.44[1.29, 1.59]), and in adults (d = 1.36[1.22, 1.50]). The moderator techniques for implanting false memories revealed a significantly lower probability of implanting false rich memory with non-directive instructions (d = 0.90[0.53, 1.27]) than with guided imagery (d = 1.45[1.32, 1.58]), or with pressure to answer (d = 1.56[1.17, 1.95]) instructions. The event emotional valence moderator exhibited the same effect for positive (d = 1.27[1.09, 1.45]) and negative valence events (d = 1.30[1.17, 1.43]).

Conclusions

The implications of the results for forensic testimony evaluation, police interrogations, and judicial cross-examination are discussed.

The Inventory of Problems-29 (IOP-29): A systematic review and bivariate diagnostic test accuracy meta-analysis

The Inventory of Problems-29 (IOP-29) is a 29-item self-administered symptom validity test (SVT) that assesses the credibility of clinical presentations related to posttraumatic stress disorder, depression/anxiety, psychosis, cognitive impairment and combination thereof. To date, no publications have summarized the classification accuracy of the IOP-29 using a bivariate meta-analytical approach that preserves the two-dimensional nature of the estimators. Our objective was to conduct a systematic review and bivariate diagnostic test accuracy meta-analysis of the IOP-29 according to the relevant guidelines. Twenty-one independent samples were included, with a total sample size of 4,163 participants. The results indicated that the IOP-29 is able to discriminate adequately between instructed simulators and healthy controls/clinical patients. Using the recommended cutoff (False Disorder Probability Score [FDS], ≥ .50), a sensitivity of 82% was achieved, maintaining specificity at 93% (false positive rate of 7%). The language of the test and the type of comparison group have been identified as possible sources of heterogeneity. Specificity decreases for the non-English version of the IOP-29, for the FDS ≥ .30, and also decreases for studies using clinical controls, for all three cutoff scores. In general, our findings support the usefulness of the IOP-29 as an SVT; however, most of the included studies use a simulation design and have been coauthored by the test authors. Likewise, about half of the studies did not include bona fide patient controls but only nonclinical controls. The results obtained are highly promising, but further research, especially that using the criterion group paradigm, is recommended. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Assessing and detecting response bias in self and referenced attitude towards conflict in family cases

Background/Objective: Contentious couple breakup is associated to adverse outcomes for couple members and offspring. Parental attitudes towards conflict resolution are a robust predictor of the litigiousness of the breakup. Nonetheless, response bias should be strongly suspected in parental attitude reported in this setting. Thus, a field study with the aim of knowing the prevalence and magnitude of the response bias and of ascertaining empirically valid criteria to classify the suspect of response bias was designed. Method: A total of 2,797 adults, 50.9 % men, with underage children aged from 21 to 68 years (M = 40.41), 2,488 married (without previous breakups), 204 involved in a mutual agreement separation and 105 in a contentious separation, answered to a measure of self-reported and referenced attitude towards conflict resolution. Results: The results exhibited that parents of the contentious and mutual agreement separation groups biased their answers. Likewise, the results provided empirical criteria for response bias classification. Epidemiologically, the observed probability of response bias was of .629[.537, .721] in the group of parents of contentious separation and of .377[.310, .444] in the group of parents of mutual agreement separation. Conclusions: The implications of the results for the design and implementation of mediation and intervention programs are discussed.

Estimating the Psychological Harm Consequence of Bullying Victimization: A Meta-Analytic Review for Forensic Evaluation

The prevalence of traditional bullying victimization has been estimated at around 36%, while that of cyberbullying has been estimated at 15%. The victimization of bullying brings with it harm to mental health that must be compensated for, after a forensic evaluation, by the aggressor or legal guardian. Thus, a meta-analytic review was undertaken with the aim of knowing the effect of bullying victimization on psychological harm, as well as quantifying the magnitude of the harm and estimating the probability that no harm associated with bullying victimization is generated.

METHOD

A random-effects correlational meta-analysis correcting effect size by sampling error and criterion and predictor unreliability was performed.

RESULTS

The results exhibited a positive (i.e., more victimization and more psychological harm) and significant mean true effect size, implying an average psychological harm associated to bullying victimization of 29.7%. Nevertheless, 26.7% of students victimized by bullying did not develop psychological harm.

CONCLUSIONS

Bullying victimization causes psychological harm, with an average increase in psychological harm associated with bullying victimization of 29.7%.

Evaluation of the Executive Functioning and Psychological Adjustment of Child-to-Parent Offenders: Epidemiology and Quantification of Harm

With the aim of ascertaining if child-to-parent offenders have impairments in the executive functions and psychological maladjustment, and to quantify the potential harm and epidemiology, a field study was designed. As for this, 76 juvenile offenders sentenced for child-to-parent violence were assessed in executive functions (Stroop tasks) and psychological adjustment (Minnesota Multiphasic Personality Inventory-Adolescent, MMPI-A). The results showed valid responses for 75 juveniles and that data were not generally biased in line with defensiveness or malingering (differential diagnosis in justice juvenile evaluations). In psychological adjustment, the results revealed a significantly higher maladjustment among offenders on all the basic clinical scales with 23% more symptoms of hysteria than the normative population, 37% more of depressive symptoms, 44% more of hypochondriac symptoms, 68% more of psychopathic deviation symptoms, 46% more of paranoid symptoms, 26% more of psychasthenic symptoms, 24% more symptoms of schizophrenia, 17% more symptoms of hypomania, and 13% more symptoms of social introversion. Epidemiologically, the prevalence rates of clinical deterioration were significantly greater than expected (0.05 in normative sample) in hypochondria (28.0%), depression (29.3%), hysteria (29.3%), psychopathic deviation (60%), paranoia (30.7%), psychasthenia (22.7%), and schizophrenia (25.3%). As for the cognitive functions, the offenders exhibited impairments estimated at 62.0% in word reading, 47.9% in color naming, 45.8% in color-word, and 11.9% in interference and a significantly higher prevalence of caseness than expected in word reading (65%), color naming (71%), and color-word (70.2%). The implications of the results for intervention are discussed.

Destrezas cognitivas en menores infractores, de protección y normalizados: un estudio de contraste

Con el objetivo de conocer si los déficits en las destrezas cognitivas son una característica común de los menores infractores y de protección (en riesgo de desviación) y diferencial de la población de menores normalizada, se diseñó un estudio de campo. Para ello, se evaluaron la inteligencia emocional, el afrontamiento, la atribución de responsabilidad y el autoconcepto, a 450 menores colombianos entre 14 y 19 años: 150 menores infractores, 150 menores de protección y 150 de población normalizada. Los resultados mostraron que los menores infractores y los de protección tenían un déficit en atención a las emociones (inteligencia emocional), recurren más a estrategias desadaptativas para la resolución de problemas y comparten una definición negativa de sí mismos, y están menos satisfechos consigo mismos y de su comportamiento. No obstante, no se observa un sesgo hacia la atribución externa de la responsabilidad. Finalmente, se cuantifica porcentualmente la magnitud de los daños en las destrezas cognitivas. Se discuten las implicaciones de los resultados para la intervención con menores infractores y el diseño de programas de prevención con menores de protección.

Assessing the effects of an education program on mental health problems in separated parents

BACKGROUND

Parental separation is a stressful experience that can lead to parents suffering mental health problems (MHPs). Parental separation education programs for coping with post-separation adjustment have proven to be effective in reducing conflict and improving co-parenting. However, the effects of these programs on MHPs have not been assessed. A field study was carried out to assess the impact of a parental separation education program on parental MHPs.

METHOD

A total of 116 separated parents who completed the program "Parental separation, not family breakdown" completed the Brief Symptom Inventory (BSI) pre- and post-intervention.

RESULTS

Separated parents had significantly higher pre-intervention scores on the nine symptom dimensions and the global indexes of distress in comparison to the normative population. The intervention yielded a significant improvement (i.e., reduction of clinical symptoms) in all MHPs, ranging from 19% in phobic anxiety to 36% in depression and general anxiety; and in the global indexes of distress (36% in the global severity index; 28% in the positive symptom distress index; and 33% in the positive symptom total). Approximately 45% of parents significantly improved through the intervention.

CONCLUSIONS

The implications of the outcomes of the separation and intervention in parents' MHPs and children wellbeing are discussed.

What and How Much Do Children Lose in Academic Settings Owing to Parental Separation?

The literature has firmly established an association between parental separation and school failure. Nevertheless, parental separation does not affect academic aptitudes. Thus, mediators explain such relationship. A field study was designed to identify and quantify damage in the mediating variables between parental separation and school failure (i.e., external school adjustment, aversion to institution, aversion to learning, aversion to instruction, aversion to teachers, indiscipline). A total of 196 children, classified into three age cohorts: 109 in level 1 (from 8 to 11 years), 46 in level 2 (from 12 to 14 years), and 41 in level 3 (15 or more years), were assessed in school adjustment and in underlying dimensions of school (mal)adjustment. The results showed significant effects of parental separation in school adjustment and in the underlying dimensions to maladjustment in the three classification levels. The magnitude of damage increased with age, i.e., small in level 1, moderate in 2, and large in 3. Damage in all the sub-dimensions underlying school (mal)adjustment was quantified. The implications of the results for the design and implementation of prevention and intervention programs for children from separated parents are discussed.

A meta-analytic review of the MMPI validity scales and indexes to detect defensiveness in custody evaluations

Background/Objective: In child custody disputes, one of the remit of the forensic psychologist is to evaluate parental attributes while suspecting defensiveness. The instrument of choice for undertaking this double task is the MMPI. Method: As to establish the state of the art on this, a meta-analysis was undertaken with a total of 32 primary studies from which 256 effect sizes were assessed. A meta-analysis was undertaken, effect sizes were corrected for sampling error and criterion unreliability. Results: The results revealed a positive, significant, large and generalizable mean true effect size for the L, K, S and MP scales, and the L + K and L + K-F indexes. The Wsd was positive, significant and large, but not generalizable. A negative and significant, but not generalizable mean true effect size was found for the F and generalizable for F-K index. The effect sizes for the L, K, S and MP scales, and the L + K and L + K-F indexes were equal. Both the gender of parents (father vs. mother) and the context of evaluation (parent child custody disputes vs. parenting capacity) were assessed as moderators. Conclusions: The results are discussed in relation to forensic practice.

Criteria-Based Content Analysis (CBCA) reality criteria in adults: A meta-analytic review

Background/Objective: Criteria-Based Content Analysis (CBCA) is the tool most extensively used worldwide for evaluating the veracity of a testimony. CBCA, initially designed for evaluating the testimonies of victims of child sexual abuse, has been empirically validated. Moreover, CBCA has been generalized to adult populations and other contexts though this generalization has not been endorsed by the scientific literature. Method: Thus, a meta-analysis was performed to assess the Undeutsch Hypothesis and the CBCA checklist of criteria in discerning in adults between memories of self-experienced real-life events and fabricated or fictitious memories. Results: Though the results corroborated the Undeutsch Hypothesis, and CBCA as a valid technique, the results were not generalizable, and the self-deprecation and pardoning the perpetrator criteria failed to discriminate between both memories. The technique can be complemented with additional reality criteria. The study of moderators revealed discriminating efficacy was significantly higher in filed studies on sexual offences and intimate partner violence. Conclusions: The findings are discussed in terms of their implications as well as the limitations and conditions for applying these results to forensic settings.

Assessing Impression Management With the MMPI-2 in Child Custody Litigation

Forensic psychological evaluation of parents in child custody litigation is primarily focused on evaluating parenting capacity and underreporting. The biased responses of underreporting have been classified as Impression Management (IM) or as Self-Deceptive Positivity (S-DP), which are regarded to be conscious or unconscious in nature, respectively. A field study was undertaken to assess impression management on the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) in child custody cases, the accuracy of the MMPI-2 scales in classifying IM, and what parents in child custody litigation actually manipulate in terms of IM. A total of 244 parents in child custody litigation and 244 parents under standard instructions were administered the MMPI-2. The results revealed that the L, Mp, Wsd, and Od scales discriminated between both samples of parents; the rate of satisfactory classification (i.e., odds ratio ranged from 5.7 for Wsd to 23.3 for Od) and an incremental validity of Od over Mp and Wsd. As for the effects of IM, the results show IM effects in the Basic Clinical Scales, the Restructured Clinical Scales, the Personality Psychopathology Five Scales, the Content Scales, and the Supplementary Scales. The implications of the results are discussed in relation to the forensic evaluation of parents in child custody litigation.

Analysis of response patterns on the MMPI-2 in psychiatric prison inmates

In order to assess mental health status, and the classification of both the overreporting and underreporting scales and indexes, 102 psychiatric prison inmates deemed mentally incompetent to stand trial completed the Spanish adaptation of the MMPI-2 under standard instructions (honest responding). The results showed patterns of consistent, non-random, nor extremely acquiescent responses. Moreover, no-outlier responses were detected. In line with the psychiatric diagnosis, all the psychiatric prison inmates were classified by the basic clinical scales as clinical cases of the psychotic dyad i.e., schizophrenia and paranoid ideation. The overreporting scales and indexes (i.e., F, K, Fb, F-K, Fp, Ds and FBS) classified the participants as malingerers, whereas the L, Wsd, and Od underreporting scales as good feigners. These scales assessing impression management i.e., consciously faking good biased responses, did not classify overreporters. Thus, they are robust indicators of honest responding among psychiatric prison inmates. The implications of these results for the practice of forensic psychology are discussed.

¿Está mediada la gravedad delictiva y cronicidad de los delincuentes juveniles por la competencia cognitivo-comportamental?

El estudio de la relación de los problemas de conducta con la competencia cognitiva y comportamental se ha convertido en un referente continuo en la literatura científica. A este respecto, los modelos de cascada/escalada en el desarrollo prevén que el nivel de problemas de conducta esté asociado al nivel de desarrollo de la competencia cognitiva y comportamental. Desde una perspectiva legal, los problemas de conducta se identifican con la delincuencia, estableciéndose niveles según la gravedad delictiva (delitos con vs. sin violencia) y del delincuente (primarios vs. reincidentes). Para comprobar si estos niveles se reflejan en la competencia cognitiva y comportamental, 283 adolescentes que estaban cumpliendo una condena judicial, 139 (68 reincidentes y 71 primarios) habían cometido un delito violento y 144 sin violencia (77 reincidentes y 67 primarios), fueron evaluados en las medidas de referencia de la competencia cognitiva y comportamental (e.g., regulación emocional, autoconcepto, atribución de la responsabilidad, resolución de problemas). Los resultados mostraron que la gravedad delictiva es independiente de la competencia cognitiva y comportamental, y que la delincuencia crónica se relaciona con menor competencia. De estos resultados se derivan consecuencias para el tratamiento de los delincuentes juveniles y para la duración de las condenas que se discuten.

Critical comparison between modified Monier-Williams and electrochemical methods to determine sulfite in aqueous solutions

In the present work, known concentration of sulfite aqueous solutions in the presence and absence of gallic acid was measured to corroborate the validity of modified Monier-Williams method. Free and bound-sulfite was estimated by differential pulse voltammetry. To our surprise, the modified Monier-Williams method (also known as aspiration method) showed to be very inaccurate for free-sulfite, although suitable for bound-sulfite determination. The differential pulse approach, using the standard addition method and a correction coefficient, proved to be swift, cheap, and very precise and accurate.

Stabilization/solidification of an alkyd paint waste by carbonation of waste-lime based formulations

The application of solvent-based paints by spraying in paint booths is extensively used in a wide range of industrial activities for the surface treatment of a vast array of products. The wastes generated as overspray represent an important environmental and managerial problem mainly due to the hazardous characteristics of the organic solvent, rendering it necessary to appropriately manage this waste. In this paper a solidification/stabilization (S/S) process based on accelerated carbonation was investigated as an immobilization pre-treatment prior to the disposal, via landfill, of an alkyd solvent-based paint waste coming from the automotive industry; the purpose of this S/S process was to immobilize the contaminants and reduce their release into the environment. Different formulations of paint waste with lime, lime-coal fly-ash and lime-Portland cement were carbonated to study the effect of the water/solid ratio and carbonation time on the characteristics of the final product. To assess the efficiency of the studied S/S process, metals, anions and dissolved organic carbon (DOC) were analyzed in the leachates obtained from a battery of compliance and characterization leaching tests. Regarding the carbonation of paint waste-lime formulations, a mathematical expression has been proposed to predict the results of the leachability of DOC from carbonated mixtures working at water/solid ratios from 0.2 to 0.6. However, lower DOC concentrations in leachates (400mg/kg DOC in L/S=10 batch leaching test) were obtained when carbonation of paint waste-lime-fly-ash mixtures was used at 10h carbonation and water to solid ratio of 0.2. The flammability characteristics, the total contents of contaminants and the contaminant release rate in compliance leaching tests provide evidence for a final product suitable for deposition in non-hazardous landfills. The characterization of this carbonated sample using a dynamic column leaching test shows a high stabilization of metals, partial immobilization of Cl(-), SO(4)(2-), F(-) and limited retention of DOC. However, the obtained results improve the previous findings obtained after the paint waste S/S using uncarbonated formulations and would be a useful pre-treatment technique of the alkyd paint waste prior to its disposal in a landfill.

[Creation and validation of a forensic protocol to assess psychological harm in battered women]

Psychological harm is one of the sequela of the victimization of a crime. Nevertheless, a diagnosis of psychological harm, that is, posttraumatic stress disorder (PTSD), does not constitute sufficient evidence alone given that, in legal terms, faking or false testimony must be detected and eliminated before an expert testimony can be admitted. To assess the aptitudes and strategies for faking psychological harm associated with domestic violence, 101 women were asked to fake psychological harm using the MMPI-2 and a forensic clinical interview. The results showed that most women (84.2%) were capable of faking in MMPI-2. The original validity scales of the MMPI-2 and their configurations were effective for the detection of faking though with a wide margin of error was observed. In the forensic clinical interview, it was much more difficult to simulate since only 3 malingerers, in which protocols were not observed any feigning strategy, were capable of simulating the psychological injury linked to domestic violence. Consequently, a multimethod approach (MMPI and interview) was contrasted and observed to classify correctly all subjects. Thus, a protocol for forensic assessment of the psychological harm consequence of domestic violence against women was formulated.

[Evaluating psychological injury in motor vehicle accidents (MVA): development and validation of a protocol for detecting pretense]

In order to assess the feigning ability of the psychological injury in a motor vehicle accident (MVA), a total of 105 subjects, which never had suffered a serious MVA and lay in psychopathology, responded to the MMPI-2 in line with the standard instructions. Thereafter, subjects were instructed to feign moral damage generated by a MVA prior to being evaluated using a clinical-forensic interview a week later, and responding to the MMPI-2 another week later. The results show that 60.9% of the subjects were able to effectively feign moral damage on the MMPI-2, and 3.8% in the forensic clinical interview. The analysis of the instruments and procedures for the validation of subject responses i.e., the original validity control scales of the MMPI-2 and the analysis of feigning strategies in the forensic clinical interview, revealed no efficacy in feigning detection. Nevertheless, collectively, all the control measures and procedures were effective for the detection of feigning. Therefore, a protocol for the detection of feigning of moral damage has been proposed.

Photochemical and photophysical studies of guanine derivatives: intermediates contributing to its photodestruction mechanism in aqueous solution and the participation of the electron adduct

The low-intensity steady-state (254 nm), microsecond flash and nanosecond (266 nm) laser photolysis of some guanine (Gua) derivatives in aqueous solution were studied. A photodestruction yield between 10(-3) and 10(-2) at a base concentration of 75 microM was determined for 254 nm irradiation at room temperature using high-performance liquid chromatography. This yield decreases with increasing purine concentration. For a similar concentration of the purine bases (2 +/- 1) x 10(-5) M, the yield increases as follows: Gua approximately 9-ethylguanine < deoxyguanosine approximately guanosine (Guo) < guanosine 5'-monophosphate. At concentrations higher than 2 x 10(-4) M the Gua derivatives' photodestruction yield seems to converge to a limiting value of the order of 10(-4). This behavior is explained in terms of self-quenching and aggregation effects which deactivate the excited states of the bases. The yields of electron photoejection have been determined in the nanosecond laser photolysis (0.083) and in the low-intensity steady-state (5.8 x 10(-3)) for Guo. Competition experiments using electron scavengers suggest that the electron adducts of the bases are one of the principal species participating in the photodestruction mechanism of these monomeric Gua. Close to 75% of the total destruction yield has contributions from initial reactions of the photojected electron at neutral pH. The quantum yield of photodestruction of Guo increases when the pH is increased as follows: 4.7 x 10(-3) (pH 1.1), 6.5 x 10(-3) (pH 2.9), 7.7 x 10(-3) (pH 7.5) and 8.1 x 10(-3) (pH 11.9). This dependence on pH and the electron scavenger experiments provide further evidence for the radical anion or its protonated form as one of the principal species involved in the photodestruction of the bases at the different pH. Under oxygen saturated conditions a 22% increase in the destruction yield is observed for Guo. However, for the dinucleotides adenylyl (3'-->5')-guanosine and thymidylyl (3'-->5')2'-deoxyguanosine, the participation of the electron is 41 and 36%, respectively, suggesting that going into a more DNA or RNA-like structure, the participation of the electron adducts species in the photodamage of DNA and RNA decreases. A mechanism of photodestruction for the Gua derivatives is proposed which takes into account these findings.

Mechanism of formation of guanine as one of the major products in the 254 nm photolysis of guanine derivatives: concentration and pH effects

The quantum yield of formation of guanine (Gua), one of the major products formed in the 254 nm steady-state photolysis of the following Gua derivatives (9-ethylguanine [9Et-Gua], deoxyguanosine [dGuo], guanosine [Guo], guanosine 5'-monophosphate [GMP]) was determined under different conditions. The formation yield increases in the following order: 9Et-Gua < dGuo approximately Guo < GMP. Electron scavengers or triplet quenchers were incorporated into the irradiated solutions with the purpose of reacting specifically with postulated or previously identified intermediates in the photolysis of Gua derivatives. A decrease in the yield of formation of Gua is observed with increasing electron scavenger concentration or with pH. These results suggest a major contribution from Gua-derivative electron adducts on the process of N(9)-R bond breakage. At an acidic pH a tautomer of the radical cation (E) of Guo is proposed as the precursor for Gua formation. The relative efficiency of the radical cation for initiating the release of free Gua depends on the pH of the solution, being less than 39% in neutral pH. Reactions from OH radicals may also result in base release as shown using N2O as additive. Finally, the formation of aggregates by the bases at concentrations used, plays an important role in the deactivation of the excited states and also in the probability of formation of the free base.

The photobiological differences of gilvocarcins V and M are not related to their transient intermediates and triplet yields

The transient absorption spectra of the intermediates produced by the 355 nm laser excitation of gilvocarcin derivatives have been investigated in various solvents. The spectra consist of a triplet-triplet absorption in the visible region and a residual absorption observed between 340 and 700 nm due to a long-lived species, assigned to the radical cation. A broad-fast decaying band with a maximum at around 700 nm attributed to the solvated electron is also seen in solutions containing a low DMSO/water volume ratio and at 266 nm irradiation of a 50% methanol/water solvent mixture. The molar absorption coefficient of the triplet state of gilvocarcin V (GV) and gilvocarcin M (GM), determined by the energy transfer method, is independent of the solvent properties and has a value of 3.0 x 10(4)/Mcm. The triplet decay rate constants for both drugs are between 1 and 5 x 10(4)/s. A similar initial yield and triplet decay rate constant of GV were observed in the presence of 3.4 mM thymine. Thus, a quenching rate constant of the GV's triplet state by thymine is estimated to be lower than 10(6)/Ms. The triplet quantum yields of both antibiotics determined by using the comparative method are higher in dimethylsulfoxide (DMSO) (0.18) than are those corresponding to 25% DMSO/water (0.06). The decrease in phi T in the presence of water could be attributed to an enhanced internal conversion rate constant from the S1 state or to an increase in the photoionization yield. The similarity of the transient intermediates and their yields for GV and GM suggest that their photobiological differences are due to other factors such as DNA binding constants, preferential localization of the drugs in the cell or the enhanced reactivity of the vinyl group toward cellular components.

Photophysical properties of gilvocarcins V and M and their binding constant to calf thymus DNA

Absorption and emission techniques were used to characterize the ground (S0), singlet (S1) and triplet states (T1) of gilvocarcin V (GV) and gilvocarcin M (GM) in different solvents. Aggregation of GV with dimerization constant equal to 7800 M-1 is observed in 10% dimethyl-sulfoxide (DMSO)/water. The photophysical properties of the S1 state of these molecules are more sensitive to changes in solvent characteristics than the corresponding ground states. The absorption of visible light by GV and GM results in a higher dipole moment of the excited state causing a red shift in the fluorescence spectra with increasing solvent polarity. The fluorescence quantum yield remains practically unchanged with changes in solvent properties unless water is present as a co-solvent. Both phi f and tau f values corresponding to GV in DMSO are larger than those of GM, whereas in 10% DMSO/H2O the opposite is observed. Thus, GV is more susceptible to other deactivation pathways besides emission in the presence of water than GM. The relative phosphorescence quantum yield (phi p = 0.03) and the triplet energy (ET = 52 kcal/mol) of GV and GM are similar. The S0-S1 energy difference is 63 kcal/mol for GV, whereas for GM it is 67. Thus, the singlet-triplet energy difference is 11 and 15 kcal/mol, respectively. The PM3/CI calculated electronic structures of these compounds are consistent with the observed photophysical properties. The dark binding constants of GV to calf thymus DNA ([1.1-0.08] x 10(6) M-1) are about an order of magnitude larger than those of GM ([0.24-0.018] x 10(6) M-1) at different ionic strengths (0-2.00 M NaCl). Also, the number of gilvocarcin molecules bound per base pair is smaller for GM than for GV. These differences in dark DNA binding parameters between GV and GM could have implications in the large photocytotoxic ability of GV as compared to GM.

The photochemistry of adenosine: intermediates contributing to its photodegradation mechanism in aqueous solution at 298 K and characterization of the major product

The steady-state (254 nm) photolysis of 9-(beta-D-erythropentofuranosyl)adenine (adenosine) in aqueous solution was studied. Photodestruction yields on the order of 1.3 x 10(-3) were determined at room temperature by measuring the initial decrease in the absorption maximum as a function of irradiation time. The use of high performance liquid chromatography (HPLC) permitted a more exact determination of the yield (2.5 x 10(-3). The formation of photoproducts was also studied using HPLC. In the photolysis of 50 microM aqueous solutions of adenosine under anaerobic conditions at least 11 stable photoproducts are formed that absorb at 260 nm, the wavelength of maximum absorption of adenosine. The major photoproduct was also isolated and characterized as adenine; its formation yield was determined to be 4.5 x 10(-4). This yield is affected by the presence of oxygen and by the initial concentration of adenosine employed. Fluorescence emission and excitation spectra were used to monitor the formation of highly fluorescent photoproducts that emit with maxima at 365, 398, and 430 nm and absorb in the wavelength region of 240-380 nm. The reactive species in the photodestruction mechanism were established using substrates that react selectively with the respective short-lived species. Photoionization is a primary photoprocess implied by these studies. The triplet state of adenosine also contributes to the photodestruction mechanism.