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1.
J Med Educ Curric Dev ; 11: 23821205241236594, 2024.
Article in English | MEDLINE | ID: mdl-38425719

ABSTRACT

OBJECTIVES: Developing professionalism is critical to medical education; accordingly, professionalism curricula may be implemented longitudinally throughout undergraduate medical education. Here we share our experiences addressing student response to medical error as a component of professionalism education during the core clerkship year. METHODS: This pretest-posttest study reports medical students' knowledge regarding learning and growing in response to medical error. Students complete an online module, Beyond Recovery: Learning and Growing in the Wake of an Error, during the Internal Medicine Clerkship. We analyzed matched pre- and posttest responses using the Wilcoxon signed-rank test. RESULTS: Pre- and posttest queries addressed 5 key elements during clinician assessment of medical error: self-expectations of perfection, long-term guilt following an error, likelihood of leaving the medical profession following an error, ability to address error with patients and families, and ability to grow in response to medical error. Results indicate students felt significantly more comfortable after completing the module in key components of managing emotions and responses in the wake of an error. CONCLUSION: Benefits observed in medical students' perspectives include improved ability to move forward following medical error, ability to engage with affected patients and families, and capacity to learn from mistakes. Despite these positives, students' high self-expectations of perfectionism were unchanged.

2.
Acad Med ; 99(2): 183-191, 2024 Feb 01.
Article in English | MEDLINE | ID: mdl-37976531

ABSTRACT

PURPOSE: To examine the relationship between the Association of American Medical Colleges (AAMC) Professional Readiness Exam (PREview) scores and other admissions data, group differences in mean PREview scores, and whether adding a new assessment tool affected the volume and composition of applicant pools. METHOD: Data from the 2020 and 2021 PREview exam administrations were analyzed. Two U.S. schools participated in the PREview pilot in 2020 and 6 U.S. schools participated in 2021. PREview scores were paired with data from the American Medical College Application Service (undergraduate grade point averages [GPAs], Medical College Admission Test [MCAT] scores, race, and ethnicity) and participating schools (interview ratings). RESULTS: Data included 19,525 PREview scores from 18,549 unique PREview examinees. Correlations between PREview scores and undergraduate GPAs ( r = .16) and MCAT scores ( r = .29) were small and positive. Correlations between PREview scores and interview ratings were also small and positive, ranging between .09 and .14 after correcting for range restriction. Small group differences in mean PREview scores were observed between White and Black or African American and White and Hispanic, Latino, or of Spanish origin examinees. The addition of the PREview exam did not substantially change the volume or composition of participating schools' applicant pools. CONCLUSIONS: Results suggest the PREview exam measures knowledge of competencies that are distinct from those measured by other measures used in medical school admissions. Observed group differences were smaller than group differences observed with traditional academic assessments and evaluations. The addition of the PREview exam did not substantially change the overall volume of applications or the proportions of out-of-state, underrepresented in medicine, or lower socioeconomic status applicants. While more research is needed, these results suggest the PREview exam may provide unique information to the admissions process without adversely affecting applicant pools.


Subject(s)
School Admission Criteria , Students, Medical , Humans , Judgment , Schools, Medical , College Admission Test
3.
J Pain Symptom Manage ; 63(4): e451-e454, 2022 Apr.
Article in English | MEDLINE | ID: mdl-34856336

ABSTRACT

This article describes a survey-based study of graduate medical residents and fellows in an integrated health system. The study explores pain curricula, learner perspectives about pain education, and learner knowledge, attitudes, and confidence. Results indicate that pain education in the graduate medical setting is inadequate to meet learner needs.


Subject(s)
Education, Medical, Graduate , Internship and Residency , Curriculum , Education, Medical, Graduate/methods , Humans , Needs Assessment , Pain/diagnosis , Pain Measurement
4.
Am J Surg ; 221(2): 291-297, 2021 02.
Article in English | MEDLINE | ID: mdl-33039148

ABSTRACT

BACKGROUND: The ACGME mandates that residency programs provide training related to high value care (HVC). The purpose of this study was to explore HVC education in general surgery residency programs. METHODS: An electronic survey was distributed to general surgery residents in geographically diverse programs. RESULTS: The response rate was 29% (181/619). Residents reported various HVC components in their curricula. Less than half felt HVC is very important for their future practice (44%) and only 15% felt confident they could lead a QI initiative in practice. Only 20% of residents reported participating in a root cause analysis and less than one-third of residents (30%) were frequently exposed to cost considerations. CONCLUSION: Few residents feel prepared to lead quality improvement initiatives, have participated in patient safety processes, or are aware of patients' costs of care. This underscores the need for improved scope and quality of HVC education and establishment of formal curricula.


Subject(s)
General Surgery/education , Internship and Residency/organization & administration , Needs Assessment/statistics & numerical data , Patient Care/standards , Quality Improvement , Adult , Curriculum/standards , Curriculum/statistics & numerical data , Female , General Surgery/economics , General Surgery/standards , General Surgery/statistics & numerical data , Health Care Costs , Humans , Internship and Residency/standards , Internship and Residency/statistics & numerical data , Male , Patient Care/economics , Patient Safety/economics , Patient Safety/standards , Practice Guidelines as Topic , Surveys and Questionnaires/statistics & numerical data
5.
J Surg Res ; 253: 34-40, 2020 09.
Article in English | MEDLINE | ID: mdl-32320895

ABSTRACT

BACKGROUND: Can factors within the Electronic Residency Application Service application be used to predict the success of general surgery residents as measured by the Accreditation Council for Graduate Medical Education (ACGME) general surgery milestones? METHODS: This is a retrospective study of 21 residents who completed training at a single general surgery residency program. Electronic Residency Application Service applications were reviewed for objective data, such as age, US Medical Licensing Examination scores, and authorship of academic publications as well as for letters of recommendation, which were scored using a standardized grading system. These factors were correlated to resident success as measured by ACGME general surgery milestone outcomes using univariate and multivariate analyses. This study was conducted at a single academic tertiary care and level 1 trauma facility. Residents who completed general surgery residency training from the years of 2012-2018 were included in the study. RESULTS: There were few correlations between application factors and resident success determined by the ACGME milestones. CONCLUSIONS: Application factors alone do not account for ongoing growth and development throughout residency. Unlike the results presented in the literature for other surgical subspecialties, predicting general surgery resident success based on application factors is not straightforward.


Subject(s)
Accreditation/statistics & numerical data , Clinical Competence/statistics & numerical data , General Surgery/education , Internship and Residency/statistics & numerical data , Job Application , Academic Medical Centers/statistics & numerical data , Adult , Female , Forecasting/methods , General Surgery/statistics & numerical data , Humans , Male , Publications/statistics & numerical data , Retrospective Studies , Tertiary Care Centers/statistics & numerical data , United States
6.
Am J Surg ; 219(2): 240-244, 2020 02.
Article in English | MEDLINE | ID: mdl-31801653

ABSTRACT

BACKGROUND: Resident autonomy is essential to the development of a surgical resident. This study aims to analyze gender differences in meaningful autonomy (MA) given to general surgery trainees intraoperatively. METHODS: This is a retrospective study of general surgery residents at an academic-affiliated tertiary care facility. Attending surgeons completed post-operative evaluations based on the Zwisch model (4-point scale, ≥3 indicating MA). RESULTS: Attending faculty members (37 males, 15 females) completed evaluations of 35 residents (18 males, 17 females). A total of 3574 evaluations were analyzed (1380 female, 2194 male residents) over 28 months. Multivariate analysis revealed case complexity, post graduate year level and rater gender were significantly associated with MA. Resident gender and faculty experience did not impact MA. CONCLUSIONS: In contrast to published literature, resident gender did not influence MA. This may be encouraging to surgical programs seeking strategies to address gender bias.


Subject(s)
Clinical Competence , General Surgery/education , Internship and Residency/organization & administration , Interprofessional Relations , Professional Autonomy , Sexism/ethics , Academic Medical Centers , Adult , Cohort Studies , Education, Medical, Graduate/methods , Female , Humans , Male , Medical Staff, Hospital , Multivariate Analysis , Operating Rooms/organization & administration , Program Evaluation , Retrospective Studies , Risk Assessment , United States
7.
J Surg Educ ; 76(6): e173-e181, 2019.
Article in English | MEDLINE | ID: mdl-31466894

ABSTRACT

OBJECTIVE: Surgical graduate medical education (GME) programs add both significant cost and complexity to the mission of teaching hospitals. While expenses tied directly to surgical training programs are well tracked, overall cost-benefit accounting has not been performed. In this study, we attempt to better define the costs and benefits of maintaining surgical GME programs within a large integrated health system. DESIGN: We examined the costs, in 2018 US dollars, associated with the surgical training programs within a single health system. Total health system expenses were calculated using actual and estimated direct GME expenses (salary, benefits, supplies, overhead, and teaching expenses) as well as indirect medical education (IME) expenses. IME expenses for each training program were estimated by using both Medicare percentages and the Medicare Payment Advisor Commission study. The projected cost to replace surgical trainees with advanced practitioners or hospitalists was obtained through interviews with program directors and administrators and was validated by our system's business office. SETTING: A physician lead, integrated, rural health system consisting of 8 hospitals, a medical school and a health insurance company. PARTICIPANTS: GME surgical training programs within a single health system's department of surgery. RESULTS: Our health system's department of surgery supports 8 surgical GME programs (2 general surgery residencies along with residencies in otolaryngology, ophthalmology, oral-maxillofacial surgery, urology, pediatric dentistry, and vascular surgery), encompassing 89 trainees. Trainees work an average of 64.4 hours per week. Total health system cost per resident ranged from $249,657 to $516,783 based on specialty as well as method of calculating IME expenses. After averaging program costs and excluding IME and overhead expenses, we estimated the average annual cost per trainee to be $84,171. We projected that replacing our surgical trainees would require hiring 145 additional advanced practitioners at a cost of $166,500 each per year, or 97 hospitalists at a cost of $346,500 each per year. Excluding overhead, teaching and IME expenses, these replacements would cost the health system an estimated additional $16,651,281 or $26,119,281 per year, respectively. CONCLUSIONS: Surgical education is an integral part of our health system and ending surgical GME programs would require large expansion of human resources and significant additional fiscal capital.


Subject(s)
Delivery of Health Care, Integrated/economics , Education, Medical, Graduate/economics , General Surgery/education , Rural Health Services/economics , Adult , Female , Humans , Internship and Residency , Male , Medicare/economics , Pennsylvania , United States
8.
Pediatr Infect Dis J ; 37(9): 943-948, 2018 09.
Article in English | MEDLINE | ID: mdl-29561514

ABSTRACT

BACKGROUND: Rotavirus vaccination was introduced in the United States in 2006. Our objectives were to examine reductions in diarrhea-associated health care utilization after rotavirus vaccine implementation and to assess direct vaccine effectiveness (VE) in US children. METHODS: Retrospective cohort study using claims data of US children under 5 years of age. We compared rates of diarrhea-associated health care utilization in prevaccine versus postvaccine introduction years. We also examined VE and duration of protection. RESULTS: Compared with the average rate of rotavirus-coded hospitalizations in the prevaccine years, overall vaccine rates were reduced by 75% in 2007 to 2008, 60% in 2008 to 2009, 94% in 2009 to 2010, 80% in 2010 to 2011, 97% in 2011 to 2012, 88% in 2012 to 2013, 98% in 2013 to 2014 and 92% in 2014 to 2015. RotaTeq-adjusted VE was 88% against rotavirus-coded hospitalization among 3-11 months of age, 88% in 12-23 months of age, 87% in 24-35 months of age, 87% in 36-47 months of age and 87% in 48-59 months of age. Rotarix-adjusted VE was 87% against rotavirus-coded hospitalization among 3-11 months of age, 86% in 12-23 months of age and 86% in 24-35 months of age. CONCLUSION: Implementation of rotavirus vaccines has substantially reduced diarrhea-associated health care utilization in US children under 5 years of age. Both vaccines provided good and enduring protection through the fourth year of life against rotavirus hospitalizations.


Subject(s)
Immunization Programs , Patient Acceptance of Health Care , Rotavirus Infections/prevention & control , Rotavirus Vaccines/therapeutic use , Vaccination Coverage/statistics & numerical data , Child, Preschool , Cohort Studies , Diarrhea/epidemiology , Diarrhea/prevention & control , Diarrhea/virology , Female , Hospitalization/statistics & numerical data , Humans , Immunization Programs/legislation & jurisprudence , Immunization Programs/statistics & numerical data , Infant , Infant, Newborn , Male , Retrospective Studies , Rotavirus , Rotavirus Infections/epidemiology , United States/epidemiology , Vaccine Potency , Vaccines, Attenuated/therapeutic use
9.
Int J Surg Case Rep ; 25: 179-83, 2016.
Article in English | MEDLINE | ID: mdl-27379750

ABSTRACT

INTRODUCTION: More than one third of Americans are obese. Obesity is a risk factor for gastroesophageal reflux disease (GERD) and esophageal adenocarcinoma (EA). The only durable treatment for morbid obesity and its comorbid conditions is bariatric surgery. There is no consensus among bariatric surgeons, however, regarding the role of preoperative screening upper endoscopy in bariatric surgery. PRESENTATION OF CASE: Two cases of incidental EA were identified by completion EGD following laparoscopic Roux-en-Y gastric bypass (LRYGB). EGD was done for anastomotic surveillance and provocative leak testing. Esophageal masses were identified and biopsies demonstrated adenocarcinoma. In both cases a laparoscopic transhiatal esophagectomy (LTHE) was completed using the gastric remnant as conduit; the biliopancreatic limb was divided proximal to the jejunojejunostomy and anastomosed to the proximal roux limb to complete the reconstruction. DISCUSSION: Obesity is a risk factor for GERD and EA. The role of EGD prior to bariatric surgery is unclear. Studies have demonstrated routine EGD prior to bariatric surgery may diagnose foregut pathology; however, few of the findings alter the planned treatment. The cost effectiveness of this strategy is questionable. There are reports of EA developing after bariatric surgery; however, we found no previous case reports of EA identified at LRYGB. CONCLUSION: Our institution has opted for selective preoperative endoscopy in patients with preoperative gastrointestinal symptoms. In post gastric bypass patients LTHE can be performed with good results.

10.
Acta Anaesthesiol Scand ; 58(10): 1214-9, 2014 Nov.
Article in English | MEDLINE | ID: mdl-25307706

ABSTRACT

BACKGROUND: Indocyanine green (ICG) is a water-soluble fluorescent dye that is bound to plasma protein when administered intravenously. Removal of ICG from the blood depends on hepatic blood flow, function of the parenchymal cells and biliary excretion. ICG elimination is described as a useful dynamic liver function test. METHODS: In this review, we looked at the most recent literature to clarify why ICG is useful in critically ill patients, the validity of the ICG plasma disappearance rate (ICG-PDR) measured transcutaneously and whether ICG-PDR has any prognostic value. CONCLUSION: In conclusion, measuring ICG-PDR is a valuable method for dynamic assessment of liver function, and is found to be a valuable prognostic tool in predicting survival for septic patients, patients presenting with acute liver failure and critically ill patients.


Subject(s)
Critical Illness , Indocyanine Green/pharmacokinetics , Liver Function Tests/methods , Coloring Agents/pharmacokinetics , Humans , Prognosis , Reproducibility of Results
11.
Int J Emerg Ment Health ; 12(4): 231-5, 2010.
Article in English | MEDLINE | ID: mdl-21870381

ABSTRACT

Military deployment of a parent carries with it a number of stresses for children, all centering around uncertainty, instability and unpredictability. This article conceptualizes military deployment and relocation stress in the context of attachment theory, and describes the types of adverse outcomes that can occur as the result of impaired attachment. It then presents a set of practical recommendations for mental health clinicians and counselors for helping children and families cope productively and negotiate the developmental hurdles associated with maintaining healthy attachment and family stability in the face of military deployment.


Subject(s)
Adaptation, Psychological , Family Therapy , Maternal Deprivation , Military Personnel/psychology , Object Attachment , Paternal Deprivation , Psychology, Military , Adult , Child , Education , Humans , Life Style , Reactive Attachment Disorder/diagnosis , Reactive Attachment Disorder/psychology , Reactive Attachment Disorder/therapy , Risk Factors , Stress Disorders, Post-Traumatic/diagnosis , Stress Disorders, Post-Traumatic/psychology , Stress Disorders, Post-Traumatic/therapy
12.
Poult Sci ; 88(11): 2324-32, 2009 Nov.
Article in English | MEDLINE | ID: mdl-19834082

ABSTRACT

It is generally accepted that the intestinal microbiota plays an important role in sustaining health and productivity of animals. Chlorella vulgaris, a naturally occurring green microalga, is believed to influence performance and health, including bird reproduction and egg quality. The nutritive value of open or indoor cultured C. vulgaris depends upon the technological process used to treat the algal mass. In the present paper, it is presented and discussed how 2 differentially processed C. vulgaris powders (spray-dried: SD-CV; bullet-milled and spray-dried: BMSD-CV) affected crop and cecal microbiota in laying hens. Polymerase chain reaction-denaturing gradient gel electrophoresis (DGGE) of bacterial 16S rRNA gene fragments was applied. The diversity of the crop universal bacterial DGGE fingerprints was not affected (6.4 +/- 1.65, 5.4 +/- 1.19, and 5.5 +/- 1.35 in the control, SD-CV, and BMSD-CV, respectively). Most of the bands from the corresponding positions in the gels were closely related to Lactobacillus sp. The DGGE fingerprints of V2-V3 fragments of 16S rRNA of crop lactobacilli had lower diversity in the control hens (8.7 +/- 1.22) than in the SD-CV (9.2 +/- 1.77) and BMSD-CV (9.9 +/- 1.88); thus, feeding C. vulgaris resulted in increased lactobacilli diversity in crop. A band closely related to Lactobacillus ingluviei was present in 9 out of 12 hens in the control group but in only 1 bird in the SD-CV and in 5 out of 11 birds in the BMSD-CV, suggesting a negative effect of C. vulgaris on this lactobacillus. Feeding C. vulgaris to laying hens also resulted in increased bacterial community diversity in the ceca. No effect of the technological processing of the microalgae on the microbial diversity could be observed. The diversity of the ceca universal bacterial DGGE fingerprints was lower in the control group than in the SD-CV and BMSD-CV (5.6 +/- 1.72 vs. 9.16 +/- 2.64 and 9.31 +/- 2.41, respectively). Most of the sequences retrieved from the DGGE bands formed ceca that were closely related to Ruminococcaceae, Lachnospiraceae, and lactobacilli, giving further insight into still poorly discovered intestinal microbiota of laying hens.


Subject(s)
Cecum/microbiology , Chickens/microbiology , Chlorella vulgaris/physiology , Crop, Avian/microbiology , Gastrointestinal Contents/microbiology , Animal Feed/analysis , Animals , Diet/veterinary , Dietary Supplements , Female , Oviposition
13.
Hip Int ; 17(3): 131-6, 2007.
Article in English | MEDLINE | ID: mdl-19197857

ABSTRACT

We studied the role of acetabulum geometry and head neck ratio in the development of osteoarthritis of the hip in young men. Contrary to previous studies we evaluated the significance of the anterior, posterior and total coverage of the femoral head, the influence of the femoral neck and the consequence of acetabular retroversion on standardized x-rays. Men aged 26-55 years who earlier had a total hip arthroplasty were included in the case group. This group was compared to a control-group of men treated as trauma patients. The study indicates that acetabular dysplasia and retroversion and a relative decreased head neck ratio are associated with osteoarthritis of the hip in young men.

14.
J Mol Biol ; 311(3): 605-21, 2001 Aug 17.
Article in English | MEDLINE | ID: mdl-11493013

ABSTRACT

The proton-conducting pathway of bacteriorhodopsin (BR) contains at least nine internal water molecules that are thought to be key players in the proton translocation mechanism. Here, we report the results of a multinuclear (1H, 2H, 17O) magnetic relaxation dispersion (MRD) study with the primary goal of determining the rate of exchange of these internal water molecules with bulk water. This rate is of interest in current attempts to elucidate the molecular details of the proton translocation mechanism. The relevance of water exchange kinetics is underscored by recent crystallographic findings of substantial variations in the number and locations of internal water molecules during the photocycle. Moreover, internal water exchange is believed to be governed by conformational fluctuations in the protein and can therefore provide information about the thermal accessibility of functionally important conformational substates. The present 2H and 17O MRD data show that at least seven water molecules, or more if they are orientationally disordered, in BR have residence times (inverse exchange rate constant) in the range 0.1-10 micros at 277 K. At least five of these water molecules have residence times in the more restrictive range 0.1-0.5 micros. These results show that most or all of the deeply buried water molecules in BR exchange on a time-scale that is short compared to the rate-limiting step in the photocycle. The MRD measurements were performed on BR solubilized in micelles of octyl glucoside. From the MRD data, the rotational correlation time of detergent-solubilized BR was determined to 35 ns at 300 K, consistent with a monomeric protein in complex with about 150 detergent molecules. The solubilized protein was found to be stable in the dark for at least eight months at 277 K.


Subject(s)
Bacteriorhodopsins/chemistry , Bacteriorhodopsins/metabolism , Halobacterium salinarum/chemistry , Water/metabolism , Detergents/metabolism , Deuterium/metabolism , Hydrogen Bonding , Kinetics , Micelles , Models, Molecular , Protein Conformation , Rotation , Solubility , Water/chemistry
15.
Methods Enzymol ; 338: 178-201, 2001.
Article in English | MEDLINE | ID: mdl-11460548

ABSTRACT

Although the MRD method has a long record in biomolecular systems, it has undergone a renaissance in the past few years as methodological developments have provided access to new types of information. In particular, MRD studies of quadrupolar nuclei such as 17O and 23Na have yielded valuable insights about the interactions of proteins and oligonucleotides with their solvent environment. The biomolecular MRD literature is still dominated by hydration studies, but the method has also been used to study the interaction of organic cosolvents and inorganic counterions with biomolecules. The MRD method can potentially make important contributions to the understanding of the mechanisms whereby protein conformational stability is affected by nonaqueous solvent components, such as denaturants, stabilizers, and helix promoters. Residence times of water molecules and other low molecular weight species in association with biomolecules can be determined by MRD. Such residence times are of general interest for understanding the kinetics of biomolecule-ligand interactions and, when exchange is gated by the biomolecule, can be used to characterize large-scale conformational fluctuations on nanosecond-millisecond time scales. By monitoring the integrity and specific internal hydration sites as well as the global solvent exposure, the MRD method can also shed light on the structure and dynamics of biomolecules in fluctuating nonnative states. Because it does not rely on high resolution, the MRD method is also applicable to very large biomolecules and complexes and has even been used to investigate protein crystals, gels, and biological tissues. In fact, dynamic studies of solids and liquid crystals were among the earliest applications of the MRD method. In many of its diverse applications, the MRD method provides unique information, complementing that available from high-resolution NMR.


Subject(s)
Nuclear Magnetic Resonance, Biomolecular/methods , Data Interpretation, Statistical , Hydrogen/chemistry , Macromolecular Substances , Models, Theoretical , Proteins/chemistry , Solutions
16.
Anticancer Res ; 21(6A): 3881-5, 2001.
Article in English | MEDLINE | ID: mdl-11911263

ABSTRACT

The amount of steroid hormone receptor proteins does not always correlate with the response of breast cancers to endocrine therapy. This may partly be due to the fact that binding of the estrogen receptor (ER) to estrogen responsive elements (ERE) of its target genes is mediated by additional cellular proteins. One of these is the high mobility group protein HMGB1, known to interact with ER thus dramatically increasing its binding to ERE. This is the first report analysing the expression patterns of HMGB1 in breast cancer cells. Northern blot analyses of the 1.4 kb and the 2.4 kb transcripts of HMGB1 in 13 breast cancer samples revealed a strong intertumoural variation by a factor of 8.5 and 14.5, respectively. This variation may contribute to the different response, of estrogen receptor-positive breast tumours to endocrine therapy, making HMGB1 a marker of considerable clinical interest.


Subject(s)
Breast Neoplasms/metabolism , HMGB1 Protein/biosynthesis , Adult , Aged , Aged, 80 and over , Blotting, Northern , Breast Neoplasms/genetics , Breast Neoplasms/pathology , Female , Gene Expression , Genetic Variation , HMGB1 Protein/genetics , Humans , Middle Aged , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , Stromal Cells/metabolism , Stromal Cells/pathology , Stromal Cells/physiology
17.
Proc Natl Acad Sci U S A ; 97(2): 629-33, 2000 Jan 18.
Article in English | MEDLINE | ID: mdl-10639130

ABSTRACT

Recent studies by x-ray crystallography, NMR, and molecular simulations have suggested that monovalent counterions can penetrate deeply into the minor groove of B form DNA. Such groove-bound ions potentially could play an important role in AT-tract bending and groove narrowing, thereby modulating DNA function in vivo. To address this issue, we report here (23)Na magnetic relaxation dispersion measurements on oligonucleotides, including difference experiments with the groove-binding drug netropsin. The exquisite sensitivity of this method to ions in long-lived and intimate association with DNA allows us to detect sequence-specific sodium ion binding in the minor groove AT tract of three B-DNA dodecamers. The sodium ion occupancy is only a few percent, however, and therefore is not likely to contribute importantly to the ensemble of B-DNA structures. We also report results of ion competition experiments, indicating that potassium, rubidium, and cesium ions bind to the minor groove with similarly weak affinity as sodium ions, whereas ammonium ion binding is somewhat stronger. The present findings are discussed in the light of previous NMR and diffraction studies of sequence-specific counterion binding to DNA.


Subject(s)
DNA/chemistry , Ions , Base Sequence , Binding Sites , Binding, Competitive , Cesium/chemistry , DNA/metabolism , Kinetics , Magnetic Resonance Spectroscopy , Netropsin/chemistry , Netropsin/metabolism , Nucleic Acid Conformation , Nucleic Acid Heteroduplexes , Oligonucleotides/chemistry , Oligonucleotides/metabolism , Potassium/chemistry , Rubidium/chemistry , Sodium/chemistry
18.
Biophys J ; 77(2): 1074-85, 1999 Aug.
Article in English | MEDLINE | ID: mdl-10423451

ABSTRACT

The orientational order and dynamics of the water molecules in form II crystals of bovine pancreatic trypsin inhibitor (BPTI) are studied by (2)H NMR in the temperature range 6-50 degrees C. From the orientation dependence of the single crystal quadrupole splitting and linewidth, the principal components of the motionally averaged quadrupole interaction tensor and the irreducible linewidth components for the orthorhombic crystal are determined. With the aid of water orientations derived from neutron and x-ray diffraction, it is shown that the NMR data can be accounted for by a small number of highly ordered crystal waters, some of which have residence times in the microsecond range. Most of these specific hydration sites must be located at intermolecular contacts. The surface hydration layer that is also present in dilute solution is likely to be only weakly ordered and would then not contribute significantly to the splitting and linewidth from the protein crystal. To probe water dynamics on shorter time scales, the (2)H longitudinal relaxation dispersion is measured for a polycrystalline BPTI sample. The observed dispersion is dominated by rapidly exchanging deuterons in protein side chains, undergoing restricted rotational motions on a time scale of 10 ns.


Subject(s)
Aprotinin/chemistry , Animals , Biophysical Phenomena , Biophysics , Cattle , Crystallization , Deuterium , Magnetic Resonance Spectroscopy , Models, Molecular , Protein Conformation , Thermodynamics , Water
19.
Protein Sci ; 8(4): 722-30, 1999 Apr.
Article in English | MEDLINE | ID: mdl-10211818

ABSTRACT

The reoccurrence of water molecules in crystal structures of RNase T1 was investigated. Five waters were found to be invariant in RNase T1 as well as in six other related fungal RNases. The structural, dynamical, and functional characteristics of one of these conserved hydration sites (WAT1) were analyzed by protein engineering, X-ray crystallography, and (17)O and 2H nuclear magnetic relaxation dispersion (NMRD). The position of WAT1 and its surrounding hydrogen bond network are unaffected by deletions of two neighboring side chains. In the mutant Thr93Gln, the Gln93N epsilon2 nitrogen replaces WAT1 and participates in a similar hydrogen bond network involving Cys6, Asn9, Asp76, and Thr91. The ability of WAT1 to form four hydrogen bonds may explain why evolution has preserved a water molecule, rather than a side-chain atom, at the center of this intricate hydrogen bond network. Comparison of the (17)O NMRD profiles from wild-type and Thr93Gln RNase T1 yield a mean residence time of 7 ns at 27 degrees C and an orientational order parameter of 0.45. The effects of mutations around WAT1 on the kinetic parameters of RNase T1 are small but significant and probably relate to the dynamics of the active site.


Subject(s)
Ribonuclease T1/chemistry , Ribonuclease T1/physiology , Schizosaccharomyces pombe Proteins , Crystallography, X-Ray , Fungal Proteins/chemistry , Hydrogen Bonding , Magnetic Resonance Spectroscopy , Models, Molecular , Mutagenesis, Site-Directed , Protein Structure, Secondary , Structure-Activity Relationship , Water/metabolism
20.
Nat Struct Biol ; 6(3): 253-60, 1999 Mar.
Article in English | MEDLINE | ID: mdl-10074944

ABSTRACT

The hydration of nonnative states is central to protein folding and stability but has been probed mainly by indirect methods. Here we use water 17O relaxation dispersion to monitor directly the internal and external hydration of alpha-lactalbumin, lysozyme, ribonuclease A, apomyoglobin and carbonic anhydrase in native and nonnative states. The results show that nonnative proteins are more structured and less solvent exposed than commonly believed. Molten globule proteins preserve most of the native internal hydration sites and have native-like surface hydration. Proteins denatured by guanidinium chloride are not fully solvent exposed but contain strongly perturbed occluded water. These findings shed new light on hydrophobic stabilization of proteins.


Subject(s)
Proteins/chemistry , Animals , Circular Dichroism , Crystallography, X-Ray , Guanidine/chemistry , Humans , Magnetic Resonance Spectroscopy , Protein Denaturation , Protein Folding , Water/chemistry
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