Sleeve Gastrectomy Compared with Gastric Bypass for Morbidly Obese Patients with End Stage Renal Disease: a Decision Analysis

INTRODUCTION

The use of bariatric surgery has increased for morbidly obese patients with end stage renal disease (ESRD) for whom listing on the waitlist is often restricted until a certain BMI threshold is achieved. Effective weight loss for this population improves access to life-saving renal transplantation. However, it is unclear whether sleeve gastrectomy (SG) vs Roux-en-Y gastric bypass (RYGB) is a more effective therapy for these patients.

METHODS

A decision analytic Markov state transition model was created to simulate the life of morbidly obese patients with ESRD who were deemed ineligible to be waitlisted for renal transplantation unless they achieved a BMI less than 35 kg/m². Life expectancy following weight management (MWM), RYGB, and SG were estimated. Base case patients were defined as having a pre-intervention BMI of 45 kg/m². Sensitivity analysis of initial BMI was performed. Markov parameters were extracted from literature review.

RESULTS

RYGB improved survival compared with SG and MWM. RYGB patients had higher rates of transplantation, leading to improved mean long-term survival. Base case patients who underwent RYGB gained 1.3 additional years of life compared with patient's who underwent SG and 2.6 additional years of life compared with MWM.

CONCLUSIONS

RYGB improves access to renal transplantation and thereby increases long-term survival compared with SG and MWM. The use of SG may be incongruent with the goal of improving access to renal transplantation for morbidly obese patients.

The metabolic time line of pancreatic cancer: Opportunities to improve early detection of adenocarcinoma

BACKGROUND

A reliable biomarker to detect pancreatic ductal adenocarcinoma (PDAC) continues to be elusive. With employing metabolomics we hypothesize that a broader analysis of systemic blood can differentiate different stages of PDAC.

METHODS

Patients undergoing pancreatic resection had plasma samples grouped by diagnosis and assayed with mass spectrometry. 10 per group [neuroendocrine (PNET), intraductal papillary mucinous neoplasm (IPMN), localized PDAC, locally advanced PDAC, and metastatic] were analyzed to assess if metabolites could delineation different stages of adenocarcinoma.

RESULTS

Of the 215 metabolites measured, four had a stronger correlation to disease burden than CA19-9. However, none of these metabolites differentiated stepwise progression in malignancy. Principal component analysis identified five metabolic components. Each cancer cohort was characterized by a unique combination of components, two components were predictors of PDCA stages.

CONCLUSIONS

Enhanced metabolomic analysis identified metabolic pathways that may assist in differentiating PDCA stages that do not occur in a linear stepwise progression.

Microfluidics contrasted to thrombelastography: perplexities in defining hypercoagulability

BACKGROUND

Elevated clot strength (maximum amplitude [MA]) measured by thrombelastography (TEG) is associated with thrombotic complications. However, it remains unclear how MA translates to thrombotic risks, as this measurement is independent of time, blood flow, and clot degradation. We hypothesize that under flow conditions, increased clot strength correlates to time-dependent measurements of coagulation and resistance to fibrinolysis.

MATERIALS AND METHODS

Surgical patients at high risk of thrombotic complications were analyzed with TEG and total thrombus-formation analysis system (T-TAS). TEG hypercoagulability was defined as an r <10.2 min, angle >59, MA >66 or LY30 <0.2% (based off of healthy control data, n = 141). The T-TAS AR and PL chips were used to measure clotting at arterial shear rates. T-TAS measurements include occlusion start time, occlusion time (OT), occlusion speed (OSp), and total clot generation (area under the curve). These measurements were correlated to TEG indices (R time, angle, MA, and LY30). Both T-TAS and TEG assays were challenged with tissue plasminogen activator (t-PA) to assess clot resistance to fibrinolysis.

RESULTS

Thirty subjects were analyzed, including five controls. TEG-defined hypercoagulability by MA was detected in 52% of the inflammatory bowel disease/cancer patients; 0% was detected in the controls. There were no TEG measurements that significantly correlated with T-TAS AR and PL chip. However, in the presence of t-PA, T-TAS AR determined OSp to have an inverse relationship with TEG angle (-0.477, P = 0.012) and LY30 (-0.449, P = 0.019), and a positive correlation with R time (0.441 P = 0.021). In hypercoagulability determined by TEG MA, T-TAS PL had a significantly reduced OT (4:07 versus 6:27 min, P = 0.043). In hypercoagulability defined by TEG LY30, T-TAS PL had discordant findings, with a significantly prolonged OT (6:36 versus 4:30 min, P = 0.044) and a slower OSp (10.5 versus 19.0 kPa/min, P = 0.030).

CONCLUSIONS

Microfluidic coagulation assessment with T-TAS has an overall poor correlation with most TEG measurements in a predominantly hypercoagulable patient population, except in the presence of t-PA. The one anticipated finding was an elevated MA having a shorter time to platelet-mediated microfluidic occlusion, supporting the role of platelets and hypercoagulability. However, hypercoagulability defined by LY30 had opposing results in which a low LY30 was associated with a longer PL time to occlusion and slower OSp. These discordant findings warrant ongoing investigation into the relationship between clot strength and fibrinolysis under different flow conditions.

Development of a Measure of Incremental Behavior Change Toward Smoking Cessation

INTRODUCTION

A reliable measure capable of detecting progression towards smoking cessation would be valuable for evaluating and optimizing the effectiveness of low- to moderate-intensity cessation interventions, such as brief advice in the primary care setting. This article presents the development and evaluation of a brief self-report measure of Incremental Behavior Change toward Smoking cessation (IBC-S).

METHODS

Sequential samples of 411 and 399 adult smokers completed items representing a spectrum of behavioral and cognitive changes antecedent to smoking cessation. The dimensionality, fit, range of difficulty, and reliability of items were evaluated using factor analysis and Rasch modeling.

RESULTS

The final 15-item IBC-S measure met fit criteria and demonstrated acceptable reliability. Participants with a significant change in IBC-S score were over four times more likely to report cessation at 6-week follow-up (OR 4.37, 95% CI 1.83-10.42).

CONCLUSION

The IBC-S is brief, reliable and associated with self-report of smoking reduction and cessation.

IMPLICATIONS

This article presents the psychometric evaluation of a measure to assess a spectrum of behaviors and cognitions antecedent to smoking cessation. The findings indicate that the items show good measurement properties and good potential as a sensitive measure to evaluate interventions. This measure provides an alternative outcome for interventions that are designed to move individuals towards cessation attempts.

Preoperative thrombelastography maximum amplitude predicts massive transfusion in liver transplantation

BACKGROUND

Massive transfusion (MT) is frequently required during liver transplantation. Risk stratification of transplant patients at risk for MT is an appealing concept but remains poorly developed. Thrombelastography (TEG) has recently been shown to reduce mortality when used for trauma resuscitation. We hypothesize that preoperative TEG can be used to risk stratify patients for MT.

MATERIAL AND METHODS

Liver transplant patients had blood drawn before surgical incision and assayed via TEG. Preoperative TEG measurements were collected in addition to standard laboratory coagulation tests. TEG variables including R-time (reaction time), angle, maximum amplitude (MA), and LY30 (clot lysis 30 min after MA) were correlated to red blood cell units, plasma (fresh frozen plasma), cryoprecipitate, and platelets during the first 24 h after surgery and tested for their performance using a receiver-operating characteristic curve.

RESULTS

Twenty-eight patients were included in the analysis with a median Model for End-Stage Liver Disease score of 17; 36% received a MT. The TEG variables associated with MT (defined as ≥10 red blood cell units/24 h) were a low MA (P < 0.001) and low angle (P = 0.014). A high international normalized ratio of prothrombin time (P = 0.003) and low platelet count (P = 0.007) were also associated with MT. MA had the highest area under the curve (0.861) followed by international normalized ratio of prothrombin time (0.803). An MA of less than 47 mm has a sensitivity of 90% and specificity of 72% to predict a MT. MA was the only coagulation variable that correlated strongly to all blood products transfused.

CONCLUSIONS

TEG MA has a high predictability of MT during liver transplantation. The use of TEG preoperatively may help guide more cost effective blood bank preparation for this procedure as only a third of patients required a MT.

Thrombelastography indicates limitations of animal models of trauma-induced coagulopathy

BACKGROUND

Thrombelastography (TEG) has been used to characterize the coagulation changes associated with injury and shock. Animal models developed to investigate trauma-induced coagulopathy (TIC) have failed to produce excessive bleeding. We hypothesize that a native TEG will demonstrate marked differences in humans compared with these experimental models, which explains the difficulties in reproducing a clinically relevant coagulopathy in animal models.

METHODS

Whole blood was collected from 138 healthy human volunteers, 25 swine and 66 Sprague-Dawley rats before experimentation. Citrated native TEGs were conducted on each whole blood sample within 2 h of collection. The clot initiation (R-time, minutes), angle (degrees), maximum amplitude (MA; millimeter), and lysis 30 min after MA (LY30; percentage) were analyzed and contrasted between species with data represented as the median and 25^th to 75^th quartile range. Difference between species was conducted with a Kruskal-Wallis test with alpha adjusted with a Bonferroni correction for multiple comparisons (alpha = 0.016).

RESULTS

Median R-time (clot initiation) was 14.65 min (IQR: 13.2-16.3 min) for humans, 5.7 min (4.9-8.8) for pigs, and 5.2 min (4.4-6) for rodents. Humans had longer R-times than both pigs (P < 0.0001) and rats (P < 0.0001); pigs were not different from rats (P = 0.4439). Angle (fibrin cross-linking) was 42.3° (interquartile range [IQR]: 37.5-50.2) for humans, 71.7° (64.3-75.6) for pigs, and 61.8° (56.8-66.7) for rats. Humans had reduced angle compared with both pigs (P < 0.0001) and rats (P < 0.0001); pigs were not different from rats (P = 0.6052). MA (clot strength) was 55.5 mm (IQR: 52.0-59.5) for humans, 72.5 mm (70.4-75.5) for pigs, and 66.5 mm (56.5-68.6) for rats. Humans had reduced MA compared with both pigs (P < 0.0001) and rats (P < 0.0001); pigs were not different from rats (P = 0.0161). LY30 (fibrinolysis) was 1.5% (IQR: 0.975-2.5) for humans, 3.3% (1.9-4.3) for pigs, and 0.5% (0.1-1.2) for rats. Humans had a lesser LY30 than pigs (P = 0.0062) and a greater LY30 than rats (P < 0.0001), and pigs had a greater LY30 than rats (P < 0.0001).

CONCLUSIONS

Humans, swine, and rodents have distinctly different coagulation systems, when evaluated by citrated native TEG. Animals are hypercoagulable with rapid clotting times and clots strengths nearly 50% stronger than humans. These coagulation differences indicate the limitations of previous models of trauma-induced coagulopathy in producing coagulation abnormalities associated with increased bleeding. The inherent hypercoagulable baseline tendencies of these animals may result in subclinical biochemical changes that are not detected by conventional TEG and should be taken into consideration when extrapolated to clinical medicine.

Fibrinolysis shutdown phenotype masks changes in rodent coagulation in tissue injury versus hemorrhagic shock

INTRODUCTION

Systemic hyperfibrinolysis (accelerated clot degradation) and fibrinolysis shutdown (impaired clot degradation) are associated with increased mortality compared with physiologic fibrinolysis after trauma. Animal models have not reproduced these changes. We hypothesize rodents have a shutdown phenotype that require an exogenous profibrinolytic to differentiate mechanisms that promote or inhibit fibrinolysis.

METHODS

Fibrinolysis resistance was assessed by thrombelastography (TEG) using exogenous tissue plasminogen activator (tPA) titrations in whole blood. There were 3 experimental groups: (1) tissue injury (laparotomy/bowel crush), (2) shock (hemorrhage to mean arterial pressure of 20 mmHg), and (3) control (arterial cannulation and tracheostomy). Baseline and 30-minute postintervention blood samples were collected, and assayed with TEG challenged with taurocholic acid (TUCA).

RESULTS

Rats were resistant to exogenous tPA; the percent clot remaining 30 minutes after maximum amplitude (CL30) at 150 ng/mL (P = .511) and 300 ng/mL (P = .931) was similar to baseline, whereas 600 ng/mL (P = .046) provoked fibrinolysis. Using the TUCA challenge, the percent change in CL30 from baseline was increased in tissue injury compared with control (P = .048.), whereas CL30 decreased in shock versus control (P = .048). tPA increased in the shock group compared with tissue injury (P = .009) and control (P = .012).

CONCLUSION

Rats have an innate fibrinolysis shutdown phenotype. The TEG TUCA challenge is capable of differentiating changes in clot stability with rats undergoing different procedures. Tissue injury inhibits fibrinolysis, whereas shock promotes tPA-mediated fibrinolysis.

A randomized trial to evaluate primary care clinician training to use the Teachable Moment Communication Process for smoking cessation counseling

OBJECTIVE

To implement and evaluate the impact of a Teachable Moment Communication Process (TMCP) training intervention on clinicians' smoking cessation counseling behaviors in practice.

METHOD

Using a group randomized trial, 31 community-based, primary care clinicians in Northeast Ohio received either TMCP training or an attention control (2010-2012). TMCP training consisted of two, three-hour sessions involving didactic instruction, skill practice with standardized patients, and coaching. Clinician performance of TMCP elements was assessed by coding audio-recordings of routine visits with smokers at baseline and post-intervention (n=806).

RESULTS

Baseline performance of all TMCP elements was similar in the two groups. After the intervention, TMCP-trained clinicians were more often observed advising patients to quit while linking smoking to the patient's concern (58% vs. 44%, p=0.01), expressing optimism (36% vs. 3%, p<0.001), expressing partnership (40% vs. 12%, p=0.003) and eliciting the patient's readiness to quit (84% vs. 65%, p=0.006) than clinicians in the comparison group. TMCP-trained clinician responses were also better aligned with patients' expressed readiness to quit smoking than comparison group clinicians (p<0.001).

CONCLUSION

The intervention significantly changed the content of clinicians' smoking cessation communication in ways consistent with the TMCP model for health behavior change.

Transitions, realignments, and focus shifts: possibilities for biopsychosocial care in the electronic health record era

The healthcare system in the United States is currently evolving in response to a diverse range of inter-related economic and political pressures. In this article, we discuss three important macro-level transitions (volume to value, clinician-centric to patient-centered care, and individual to population) and their implications for the practice of medicine, health information technology (HIT), and clinical training. Specifically, challenges and opportunities for advancing the use of the biopsychosocial model in clinical practice and teaching in this new, electronic health record (EHR) era of medicine are highlighted. While much work needs to be done to leverage the potential of EHR/HIT systems, their potential to improve population health and patient experience while controlling the costs of care is great. As primary care clinicians and behavioral scientists navigating this changing healthcare landscape, we should continue to strive to deliver high-quality, patient-centered care. Insisting that future generations of EHR/HIT systems support a biopsychosocial approach is part of this mission.

How well do physician and patient visit priorities align?

This study found that there is alignment between a patient's reason for a visit and the physician's main concern 69% of the time. Less than fully aligned priorities were associated with insurance status and the number of problems addressed.

Teachable moments for health behavior change and intermediate patient outcomes

OBJECTIVE

Teachable moments (TM) are opportunities created through physician-patient interaction and used to encourage patients to change unhealthy behaviors. We examine the effectiveness of TMs to increase patients' recall of advice, motivation to modify behavior, and behavior change.

METHODS

A mixed-method observational study of 811 patient visits to 28 primary care clinicians used audio-recordings of visits to identify TMs and other types of advice in health behavior change talk. Patient surveys assessed smoking, exercise, fruit/vegetable consumption, height, weight, and readiness for change prior to the observed visit and 6-weeks post-visit.

RESULTS

Compared to other identified categories of advice (i.e. missed opportunities or teachable moment attempts), recall was greatest after TMs occurred (83% vs. 49-74%). TMs had the greatest proportion of patients change in importance and confidence and increase readiness to change; however differences were small. TMs had greater positive behavior change scores than other categories of advice; however, this pattern was statistically non-significant and was not observed for BMI change.

CONCLUSION

TMs have a greater positive influence on several intermediate markers of patient behavior change compared to other categories of advice.

PRACTICE IMPLICATIONS

TMs show promise as an approach for clinicians to discuss behavior change with patients efficiently and effectively.

Creating a culture of inquiry in family medicine

BACKGROUND AND OBJECTIVES

Strengthening the contribution of reflective practice and new knowledge generation to the learning relationships forged during graduate and undergraduate medical training offers a possibility to create a climate more conducive to the recruitment and retention of family physicians. The Culture of Inquiry (CI) fellowship, an immersive, experientially based training program, combines didactic instruction, workshops, and mentoring to develop the capacity of family medicine's teachers to imagine, implement, and disseminate clinically relevant research and stimulate collaborations with those whom they train. This article outlines the CI fellowship program, summarizes its outcomes, and offers insights about programmatic features contributing to its success.

METHODS

The Department of Family Medicine and Community Health at Case Western Reserve University selected CI fellows from interested local family physicians who train residents and medical students. Over 10 months, with 10% effort expected from fellows, the CI fellowship exposed each fellow to the entire research process and provided technical and logistical support for the design and completion of two research projects. Quantitative and qualitative program evaluation were used to assess outcomes.

RESULTS

Scholarly productivity of fellows exceeded expectations. Collaborations with students and residents produced a ripple effect that amplified the fellowship's impact by strengthening those relationships crucial to the creation of a culture of inquiry among family medicine's teachers, learners, and practitioners.

CONCLUSIONS

The CI fellowship represents a highly replicable program to connect committed and interested clinicians to research mentors with the goal of increasing scholarship and creating a growing culture of inquiry in family medicine.

The effect of insurance-driven medication changes on patient care

PURPOSE

Insurance plans periodically change their formularies to enhance medical efficacy and cost savings. Patients face challenges when formulary changes affect their treatment. This study assessed the impact of insurance-driven medication changes on primary care patients and examined implications for patient care.

METHODS

We mailed questionnaires to a cross-sectional random sample of 1200 adult patients who had visited one of 3 family medicine practices within the past 6 months, asking them to describe problems they had encountered in filling medication prescriptions. We performed descriptive analyses of the frequency and distribution of demographic variables and conditions being treated. Using logistic regression analysis, we identified demographic and health-related variables independently associated with patient-reported problems caused by formulary changes.

RESULTS

Three variables-a greater number of prescription medications taken, younger patient age, and reliance on government insurance-were independently associated with an increased likelihood of encountering a problem filling a medication. Patients who reported an insurance-related issue filling a new or existing prescription over the past year (23%) encountered an average of 3 distinct problems. Patients experienced adverse medical outcomes (41%), decreased satisfaction with the health care system (68%), and problems that burdened the physician practice (83%). Formulary changes involving cardiac/hypertension/lipid and neurologic/psychiatric medications caused the most problems.

CONCLUSIONS

Insurance-driven medication changes adversely affect patient care and access to treatment, particularly for patients with government insurance. A better understanding of the negative impact of formulary changes on patient care and indirect health care expenditures should inform formulary change practices in order to minimize cost-shifting and maximize continuity of care.

Identifying teachable moments for health behavior counseling in primary care

OBJECTIVE

Situations with potential to motivate positive change in unhealthy behavior have been called 'teachable moments'. Little is known about how they occur in the primary care setting.

METHODS

Cross-sectional observational design. Audio-recordings collected during 811 physician-patient interactions for 28 physicians and their adult patients were analyzed using conversation analysis.

RESULTS

Teachable moments were observed in 9.8% of the cases, and share three features: (1) the presence of a concern that is salient to the patient that is either obviously relevant to an unhealthy behavior, or through conversation comes to be seen as relevant; (2) a link that is made between the patient's salient concern and a health behavior that attempts to motivate the patient toward change; and (3) a patient response indicating a willingness to discuss and commit to behavior change. Additionally, we describe phenomena related to, but not teachable moments, including teachable moment attempts, missed opportunities, and health behavior advice.

CONCLUSIONS

Success of the teachable moment rests on the physician's ability to identify and explore the salience of patient concerns and recognize opportunities to link them with unhealthy behaviors.

PRACTICE IMPLICATIONS

The skills necessary for accomplishing teachable moments are well within the grasp of primary care physicians.

Development of an instrument to document the 5A's for smoking cessation

BACKGROUND

The widely recommended 5A's strategy for brief smoking cessation includes five tasks: Ask, Advise, Assess, Assist, and Arrange. Assessments of the 5A's have been limited to medical-record review and self-report. Using observational data, an instrument to assess the rate at which the 5A's are accomplished was developed.

METHODS

The 5A's Direct Observation Coding scheme (5A-DOC) was developed using published 5A's guidelines and was refined using observed clinician-patient interactions. The development sample consisted of 46 audio-recorded visits of smokers with their physician (n=5), collected in 2000. The 5A-DOC was next applied to a second sample of 131 visits with 28 physicians between 2005 and 2008. Inter-rater reliability was assessed and frequencies reported. Analyses were completed in 2008.

RESULTS

Three observations shaped the development of the 5A-DOC: (1) patients accomplish 5A's tasks; (2) some communication actions accomplish multiple 5A's tasks simultaneously; and (3) sequence is important. Inter-rater agreement for identifying each task was moderate to excellent (kappa=0.58-1.0). When smoking status was established (Ask, n=78), 61% Assessed readiness, and 50% contained Assist. In all, 73% failed to complete the 5A's adequately.

CONCLUSIONS

Accounting for patient activity in smoking-cessation discussions is essential to accurately capture the degree to which the 5A's have been accomplished. The 5A-DOC can be applied to audio or transcript data to reliably assess which of the 5A's tasks have been accomplished. Clinician performance of the 5A's was modest, and findings suggest that clinician training should focus on Assess and the timing of this task, and alignment with patients' reported readiness.

Teachable moments for health behavior change: a concept analysis

OBJECTIVE

"Teachable moments" have been proposed as events or circumstances which can lead individuals to positive behavior change. However, the essential elements of teachable moments have not been elucidated. Therefore, we undertook a comprehensive review of the literature to uncover common definitions and key elements of this phenomenon.

METHODS

Using databases spanning social science and medical disciplines, all records containing the search term "teachable moment*" were collected. Identified literature was then systematically reviewed and patterns were derived.

RESULTS

Across disciplines, 'teachable moment' has been poorly developed both conceptually and operationally. Usage of the term falls into three categories: (1) "teachable moment" is synonymous with "opportunity" (81%); (2) a context that leads to a higher than expected behavior change is retrospectively labeled a 'teachable moment' (17%); (3) a phenomenon that involves a cueing event that prompts specific cognitive and emotional responses (2%).

CONCLUSION

The findings suggest that the teachable moment is not necessarily unpredictable or simply a convergence of situational factors that prompt behavior change but suggest the possible creation of a teachable moment through clinician-patient interaction.

PRACTICE IMPLICATIONS

Clinician-patient interaction may be central to the creation of teachable moments for health behavior change.

An outbreak of Legionella longbeachae infection in an intensive care unit?

During a nine-day period, five patients in a 14-bed intensive care unit (ICU) were shown to have seroconverted with a four-fold or greater rise in serum antibody titre to Legionella longbeachae serogroup 1. A further two patients were observed to have high titres consistent with previous exposure but earlier serum samples were not available for comparison. No patients had antibody responses to Legionella pneumophila serogroups 1 and 2. L. longbeachae was not cultured from respiratory secretions from patients or from the environment within the unit. Legionella anisa was recovered from one cooling tower on the ninth floor of the tower block. The ICU is located on the first floor of the same tower and receives external air from two vents, one on the eastern and the other on the western aspect. All patients with serological evidence of L. longbeachae infection were concomitantly infected with multiresistant Staphylococcus aureus, and were located in bays on the eastern side of the unit. A large pigeon nest was discovered within 1-2 m of the eastern vent. Following removal of the birds' nest, no further cases were seen on routine screening of all patients within the unit over the next eight weeks. Alternatively, seroconversion may have been related to demolition of the adjacent nine-storey nurses home. This was begun one month before the first case was diagnosed and was completed four months later. The periodic northerly winds could have carried legionellae from the demolition site directly over the block housing the ICU and may have concentrated them near the eastern air vent. All patients had pneumonia, which was probably multifactorial in origin. There is some uncertainty whether the serological responses seen were an epiphenomenon or were truly indicative of infection with L. longbeachae.

Evaluation of bacteriological transport swabs

Ten commercial transport swabs were evaluated for their ability to preserve bacteria for 24 and 48 hours. Microorganisms included ATCC strains of Gram-positive and Gram-negative aerobes and anaerobes. There was a wide variation in performance. Swabs using Amies plus charcoal medium or Stuart's medium had better recovery rates than those using Amies medium alone. The nature of the tips of the swabs had little influence. Performance was not correlated with cost of the swabs. These data will assist institutions to make cost-effective decisions when purchasing bacteriological transport systems.

Circular dichroism spectra of amino acid complexes. II. Chelated amino acid complexes with the CoN5O chromophore

The circular dichroism spectra of a series of optically active (α-aminocarboxylato)tetraamminecobalt(111) complexes have been measured in aqueous solution, and in the presence of salts of polarizable anions. The observed spectra in the visible region have been analysed to determine the signs of the Cotton effects of the three components of the 1A1g ↔ 1T1g cobalt(111) transition. For L-amino acids, the transition with A2g(D4h) parentage is negative, and the two transitions with Eg(D4h) parentage have opposite signs. Published circular dichroism spectra of complexes of the type [Co(en)2(L-am)]2+ were similarly interpreted in terms of a perturbed tetragonal chromophore, and it was shown that the vicinal effect of the L-amino acids imposed the same signs onto the component transitions as for the tetraammines and for a similar series of pentaamminecobalt(111) complexes.