"We're all truly pulling in the exact same direction": A qualitative study of attending and resident physician impressions of structured bedside interdisciplinary rounds

BACKGROUND

Physicians often hold leadership roles in implementing interdisciplinary rounds (IDR) in clinical settings, thus understanding physician perspectives of bedside IDR is crucial.

OBJECTIVE

To understand physicians' perspectives of structured bedside IDR.

DESIGN

Qualitative descriptive study.

SETTING AND PARTICIPANTS

Medical and transitional year resident and hospitalist physicians participating in structured bedside IDR in a community teaching hospital affiliated with a large academic center.

METHODS

We conducted semi-structured interviews and focus groups with study participants about their experiences with participating in structured bedside IDR between July 2017 and April 2018. All interviews were recorded and professionally transcribed. We used thematic analysis to identify key themes.

RESULTS

We interviewed 41 resident physicians and 10 hospitalist physicians and discovered five key themes that highlight physician impressions of bedside IDR. Bedside IDR decreased unnecessary care, screened for risks/errors, created a shared mental model of care, and increased physician empathy for the patient and the interprofessional care team. Physicians felt patients valued the streamlined communication they experienced but questioned the intrusiveness of large healthcare teams. Challenges to bedside IDR included the meaningful engagement of key stakeholders and, particularly for resident physicians, the difficultly of managing unstandardized communication in a standardized time-sensitive setting.

CONCLUSIONS

Structured bedside IDR have the capacity to improve patient care, interprofessional teamwork, and physician empathy for patients and the interprofessional team. However, sustained leadership support and clearly defined rounds goals and objectives are necessary ingredients to maximize the benefits and address the challenges of bedside IDR.

Palliative Care across Settings: Perspectives from Inpatient, Primary Care, and Home Health Care Providers and Staff

BACKGROUND

Early introduction of palliative care can improve patient-centered outcomes for older adults with complex medical conditions. However, identifying the need for and introducing palliative care with patients and caregivers is often difficult. We aim to identify how and why a multi-setting approach to palliative care discussions may improve the identification of palliative care needs and how to facilitate these conversations.

METHODS

Descriptive qualitative study to inform the development and future pilot testing of a model to improve recognition of, and support for, unmet palliative care needs in home health care (HHC). Thematic analysis of semi-structured interviews with providers across inpatient (n = 11), primary care (n = 17), and HHC settings (n = 10).

RESULTS

Four key themes emerged: 1) providers across settings can identify palliative care needs using their unique perspectives of the patient's care, 2) identifying palliative care needs is challenging due to infrequent communication and lack of shared information between providers, 3) importance of identifying a clinical lead of patient care who will direct palliative care discussions (primary care provider), and 4) importance of identifying a care coordination lead (HHC) to bridge communication among multi-setting providers. These themes highlight a multi-setting approach that would improve the frequency and quality of palliative care discussions.

CONCLUSIONS

A lack of structured communication across settings is a major barrier to introducing and providing palliative care. A novel model that improves communication and coordination of palliative care across HHC, inpatient and primary care providers may facilitate identifying and addressing palliative care needs in medically complex older adults.

Care challenges of home health patients living with dementia: a pathway forward with palliative care

BACKGROUND

Home health care (HHC) is a leading source of care support for older adults with serious illness, particularly patients living with dementia (PLWD). Demand for HHC is expected to continue to grow, driven by an aging population and preference for non-institutional care. HHC agencies are frequently under pressure to find effective approaches for improving care delivery and quality. One strategy that has the potential to improve the quality of life and patient satisfaction in HHC for PLWD is the integration of palliative care. Therefore, we sought to understand the experiences and needs of PLWD and their family caregivers specifically focusing on ways that HHC and palliative care may be integrated as part of the care transition from hospital to home, to better support PLWD and their families.

METHODS

We conducted a descriptive qualitative study focusing on the perspectives of patients, caregivers, and healthcare team members about palliative care delivery for patients receiving HHC. Interviews were audio-recorded and professionally transcribed. In this analysis, we specifically report on dementia-related content using an iterative, team-based thematic analysis approach.

RESULTS

We identified three themes: 1) 'Living in the Whirlwind' which describes the many competing demands on caregivers time and the associated feeling of loss of control, 2) 'Thinking Ahead' which describes the importance of thinking beyond the day-to-day tasks to begin planning for the future, and 3) 'Pathways Forward' which describes the integration of palliative care into HHC to provide enhanced support for PLWD and their caregivers.

CONCLUSION

In this qualitative study, our formative work identified the importance of providing anticipatory guidance (e.g., safety, advance care planning) coupled with emotional and pragmatic care supports (e.g., finding resources, navigating insurance) to sustain caregivers who are struggling with the whirlwind.

Frontline healthcare workers' perspectives on interprofessional teamwork during COVID-19

Effective interprofessional teamwork serves an important role in successful crisis response. Responses to past public health crises have relied on interprofessional communication and trust to support healthcare worker (HCW) resiliency. To understand interprofessional interactions and perceptions of teamwork during the COVID-19 response, we conducted in-depth semi-structured interviews with 18 inpatient HCWs (11 bedside nurses, 5 care coordinators, and 2 pharmacists) from one VA Medical Center between March and June 2020. Using thematic analysis, we identified four key themes that describe the strengths and challenges of interprofessional teamwork, communication, patient care, and organizational response during the initial COVID-19 surge. Interprofessional teams were fragmented. HCWs who transitioned to remote work lost their status on inpatient teams and struggled to provide pre-pandemic levels of quality of care. Conversely, interprofessional teamwork improved for HCWs who continued to work on inpatient units, where study participants described a decline in interprofessional hierarchies and an increase in mutual support. Participants described the need for timely, accurate, transparent communication as they faced new patient safety and communication challenges brought on by the pandemic. HCWs expressed a desire for sustained leadership support and inclusion in institutional decision-making. The challenges to teamwork, communication, and patient care reported in this study highlight the need for consistent, transparent communication and organizational response from hospital leadership during times of crisis.

"Our Hands Are Tied Until Your Doctor Gets Here": Nursing Perspectives on Inter-hospital Transfers

BACKGROUND

The transfer of patients between hospitals (inter-hospital transfer, or IHT) is a common occurrence for patients, but guidelines to ensure safe and effective IHTs are lacking. Poor IHTs result in higher rates of mortality, longer lengths of stay, and higher hospitalization costs compared to admissions from the emergency department. Nurses are often the first point of contact for IHT patients and can provide valuable insights on key challenges to IHT processes.

OBJECTIVE

To characterize the experiences of inpatient floor-level bedside nurses caring for IHT patients and identify care coordination challenges and solutions.

DESIGN/PARTICIPANTS/APPROACH

Qualitative study using semi-structured focus groups and interviews conducted from October 2019 to July 2020 with 21 inpatient floor-level nurses caring for adult medicine patients at an academic hospital. Nurses were recruited using a purposive convenience sampling approach. A combined inductive and deductive coding approach guided by thematic analysis was used for data analysis.

KEY RESULTS

Results from this study are mapped to the Agency for Healthcare Research and Quality Care Coordination Measurement Framework domains of communication, assessing needs and goals, and negotiating accountability. The following key themes characterize nurses' experiences with IHT related to these domains: (1) challenges with information exchange and team communication during IHT, (2) environmental and information preparation needed to anticipate transfers, and (3) determining responsibility and care plans after the IHT patient has arrived at the accepting facility.

CONCLUSIONS

Nurses described the absence of standardized processes to coordinate care before or at the time of patient arrival. Challenges to communication and coordination during IHTs negatively impacted patient care and nursing professional satisfaction. To streamline care for IHT patients and reduce nursing stress, future IHT interventions should include standardized handoff reports, timely identification and easy access to admitting clinicians, and timely clinician evaluation and orders.

Forgotten frontline workers: Environmental health service employees' perspectives on working during the COVID-19 pandemic

BACKGROUND

Environmental Health Service employees (EVS) sanitize healthcare facilities and are critical to preventing infection, but are under-resourced during the COVID-19 pandemic and at risk of burnout.

OBJECTIVE

Understand demands on EVS' work and strain on resources during COVID-19.

DESIGN

Qualitative descriptive study conducted in winter 2020-2021.

SETTING

One quaternary care academic medical center in Colorado.

PARTICIPANTS

A convenience sample of 16 EVS out of 305 eligible at the medical center. Fifty percent identified as Black, 31% as Hispanic, 6% as Asian, and 6% as White (another 6% identified as mixed race). Sixty-nine percent were female, and half were born in a country outside the United States.

MEASURES

Semistructured telephone interviews. Interviews were audio-recorded and transcribed, and thematic analysis was used to identify key themes.

RESULTS

Four themes illustrate EVS experiences with job strain and support during COVID-19: (1) Needs for ongoing training/education, (2) Emotional challenges of patient care, (3) Resource/staffing barriers, and (4) Lack of recognition as frontline responders. Despite feeling unrecognized during the pandemic, EVS identified structural supports with potential to mitigate job strain, including opportunities for increased communication with interdisciplinary colleagues, intentional acknowledgment, and education for those who speak languages other than English. Strategies that can increase physical and emotional resources and reduce job demands have potential to combat EVS burnout.

CONCLUSIONS

As the surge of COVID-19 cases continues to overwhelm healthcare facilities, healthcare systems and interdisciplinary colleagues can adopt policies and practices that ensure lower-wage healthcare workers have access to resources, education, and emotional support.

Care planning priorities of older patients with advanced bladder cancer

OBJECTIVES

Advanced bladder cancer (ABC) disproportionately affects older adults, and little is known about older patients' priorities for care planning in advanced cancer. Patient-centered communication remains crucial to shared decision-making between patients, families, and providers. Yet, older patients with cancer may not always know how to express their preferences, and oncologists do not always review patients' informational needs. This study aimed to understand preferences of older patients with ABC related to their communication with providers and navigation of care planning.

MATERIALS AND METHODS

This qualitative descriptive study involved in-depth interviews and focus groups with older patients with ABC and their care partners, which explored their priorities for care planning and communication with providers, decision-making processes, and valued traits in ABC care. Data were analyzed using thematic analysis.

RESULTS

Ten participants attended focus groups or interviews. Seven patients were male and three care partners were female. The mean age was 74. Time since ABC diagnosis ranged from three to seventeen months. Four key themes illustrate participants' priorities in their ABC care as older adults: 1. The significance of key phrasing in communication from oncologists, 2. The need for clear expectation-setting about prognosis and treatment, 3. The role of others in patient care decisions, and 4. Valued traits in care communication.

CONCLUSION

Older patients with ABC and their care partners are active participants in their care. Oncologists should prioritize setting clear expectations for treatment, involving family in care planning, and communicating honestly about expected changes to quality of life and functional status.

Resident perspectives on the value of interdisciplinary conference calls for geriatric patients

BACKGROUND

There are limited competency-based educational curricula for transitions of care education (TOC) for internal medicine (IM) residency programs. The University of Colorado implemented a virtual interdisciplinary conference call, TEAM (Transitions Expectation and Management), between providers on the inpatient Acute Care of the Elder (ACE) unit and the outpatient Seniors Clinic at the University of Colorado Hospital. Residents rotating on the ACE unit participated in weekly conferences discussing Seniors Clinic patients recently discharged, or currently hospitalized, to address clinical concerns pertaining to TOC. Our goals were to understand resident perceptions of the educational value of these conferences, and to determine if these experiences changed attitudes or practice related to care transitions.

METHODS

We performed an Institutional Review Board-approved qualitative study of IM housestaff who rotated on the ACE unit during 2018-2019. Semi-structured interviews were conducted to understand perceptions of the value of TEAM calls for residents' own practice and the impact on patient care. Data was analyzed inductively, guided by thematic analysis.

RESULTS

Of the 32 IM residents and interns who rotated on ACE and were invited to participate, 11 agreed to an interview. Three key themes emerged from interviews that highlighted residents' experiences identifying and navigating some of their educational 'blind spots:' 1) Awareness of patient social complexities, 2) Bridging gaps in communication across healthcare settings, 3) Recognizing the value of other disciplines during transitions.

CONCLUSIONS

This study highlights learner perspectives of the benefit of interdisciplinary conference calls between inpatient and outpatient providers to enhance transitions of care, which provide meaningful feedback and serve as a vehicle for residents to recognize the impact of their care decisions in the broader spectrum of patients' experience during hospital discharge. Educators can maximize the value of these experiences by promoting reflective debriefs with residents and bringing to light previously unrecognized knowledge gaps around hospital discharge.

Social Media Perceptions of Legacy-Making: A Qualitative Analysis

Background: Individuals with life-limiting illnesses experience psychotherapeutic benefits of transmitting their life's history to loved ones; however, the scope and depth of what warrants preservation and who ought to undertake such activity remains less clear. Furthermore, individuals with conditions that afflict the brain face barriers regarding the timing and structure of such interventions. We analyzed data from an online social media forum to understand perceptions of legacy-making.

Methods: This is a qualitative descriptive study of Slashdot, a social media website with a focus on science, technology, and politics. In August 2010, a Slashdot user inquired about a loved one with a life-limiting illness and asked for opinions on how to preserve the individual's memories. We conducted a content analysis of the individual comments related to digital legacy-making to identify common themes.

Results: Slashdot users contributed 527 replies to the initial inquiry. Users often included bereaved individuals who offered input on the need to preserve information about a loved one, the modalities in which to preserve, and what type of content to preserve. Three key themes emerged related to legacy-making: (1) capture the individual's essence and avoid the minutia, (2) live for now to avoid prolonged suffering, and (3) recognize the equal benefits to all who memorialize.

Conclusions: Users in a social media forum articulated the value of capturing their loved ones' essence for posterity, which many believed would help them to avoid prolonged grief. These findings have implications for the development and timing of personalized psychosocial interventions as well as informing application development of evidence-based digital legacy systems.

Optimizing future planning in Parkinson disease: suggestions for a comprehensive roadmap from patients and care partners

BACKGROUND

Living with Parkinson disease (PD) is complicated by an unpredictable disease course which can delay planning for future needs. This study explores patient and care partner needs related to future planning using a palliative care framework with physical, psychological, social, cultural, end-of-life, and ethical aspects of care in PD to guide analysis.

METHODS

Secondary analysis of patient and care partner interviews from a randomized clinical trial comparing interdisciplinary outpatient palliative care versus standard care for individuals with PD and care partners in an academic setting. Sixty participants were interviewed (30 patients and 30 care partners) about needs related to future planning. Team-based thematic analysis was used to identify key themes.

RESULTS

Many care partners and patients living with PD described a desire for information about what to expect and how to plan for the future. Participants posed multiple questions about PD progression and devised the metaphor of a "roadmap" as a guide for decision making and planning. When exploring the concept of a PD roadmap, five themes emerged: (I) desire for a comprehensive tool for future planning, such as a roadmap, (II) care partner preferences for specific future planning, (III) PD-related life changes as opportunity for future planning and decision-making, (IV) cues from family, peers, and medical professionals about "location" on the roadmap, and (V) opportunities and challenges to integrating a PD roadmap into patient-centered care.

CONCLUSIONS

Patients and care partners described key needs related to future planning that can inform a comprehensive roadmap to assist with education, communication, and decision making. A roadmap tool can promote individualized anticipatory guidance and multidimensional shared decision-making discussions between patients, care partners, and the healthcare team related to PD progression.

Community-Based Conversations about Advance Care Planning for Underserved Populations Using Lay Patient Navigators

Background: Widespread community engagement in advance care planning (ACP) is needed to overcome barriers to ACP implementation. Objective: Develop, implement, and evaluate a model for community-based ACP in rural populations with low English language fluency and health care access using lay patient navigators. Design: A statewide initiative to improve ACP setting/subjects-trained in a group session approach, bilingual patient navigators facilitated 1-hour English and Spanish ACP sessions discussing concerns about choosing a surrogate decision maker and completing an advance directive (AD). Participants received bilingual informational materials, including Frequently Asked Questions, an AD in English or Spanish, and Goal Setting worksheet. Measurement: Participants completed a program evaluation and 4-item ACP Engagement Survey (ACP-4) postsession. Results: For 18 months, 74 ACP sessions engaged 1034 participants in urban, rural, and frontier areas of the state; 39% were ethnically diverse, 69% female. A nurse or physician co-facilitated 49% of sessions. Forty-seven percent of participants completed an ACP-4 with 29% planning to name a decision maker in the next 6 months and 21% in the next 30 days; 31% were ready to complete an AD in the next 6 months and 22% in the next 30 days. Evaluations showed 98% were satisfied with sessions. Thematic analysis of interviews with facilitators highlighted barriers to delivering an ACP community-based initiative, strategies used to build community buy-in and engagement, and ways success was measured. Conclusion: Patient navigators effectively engaged underserved and ethnically diverse rural populations in community-based settings. This model can be adapted to improve ACP in other underserved populations.

Framing advance care planning in Parkinson disease: Patient and care partner perspectives

OBJECTIVE

Advance care planning (ACP) is a core quality measure in caring for individuals with Parkinson disease (PD) and there are no best practice standards for how to incorporate ACP into PD care. This study describes patient and care partner perspectives on ACP to inform a patient- and care partner-centered framework for clinical care.

METHODS

This is a qualitative descriptive study of 30 patients with PD and 30 care partners within a multisite, randomized clinical trial of neuropalliative care compared to standard care. Participants were individually interviewed about perspectives on ACP, including prior and current experiences, barriers to ACP, and suggestions for integration into care. Interviews were analyzed using theme analysis to identify key themes.

RESULTS

Four themes illustrate how patients and care partners perceive ACP as part of clinical care: (1) personal definitions of ACP vary in the context of PD; (2) patient, relationship, and health care system barriers exist to engaging in ACP; (3) care partners play an active role in ACP; (4) a palliative care approach positively influences ACP. Taken together, the themes support clinician initiation of ACP discussions and interdisciplinary approaches to help patients and care partners overcome barriers to ACP.

CONCLUSIONS

ACP in PD may be influenced by patient and care partner perceptions and misperceptions, symptoms of PD (e.g., apathy, cognitive dysfunction, disease severity), and models of clinical care. Optimal engagement of patients with PD and care partners in ACP should proactively address misperceptions of ACP and utilize clinic teams and workflow routines to incorporate ACP into regular care.

Patient Perspectives on Advance Care Planning via a Patient Portal

BACKGROUND

Patient portals can offer patients an opportunity to engage in the advance care planning (ACP) process outside of clinical visits.

OBJECTIVE

To describe patient perspectives on use of patient portal-based ACP tools.

DESIGN

Interviews with patients who used portal-based ACP tools. The tools included an electronic Medical Durable Power of Attorney (MDPOA) form to designate a medical decision maker, a patient-centered educational web page, online messaging, and patient access to completed advance directives stored in the electronic health record (EHR).

SETTING

Regional health-care system with a common EHR.

MEASUREMENTS

Semistructured interviews with purposefully sampled patients who used the ACP tools. Questions explored motivations for using the tools and perceptions about how the tools fit into ACP. Analysis followed a grounded hermeneutic editing approach.

RESULTS

From 46 patients (mean age: 49, 63% female), 4 key themes emerged: (1) individualized explorations of the ACP tools, (2) personal initiation and engagement with ACP tools through the portal, (3) value of connecting ACP portal tools to clinical care, and (4) practicality of the ACP tools. Patients described benefits of communicating with health-care team members who referred them to online ACP tools, as well as having the electronic MDPOA form connected to clinical care.

CONCLUSIONS

Patients considered the portal-based ACP tools to be practical and feasible to use within the scope of their own ACP experiences. Further study is needed to understand whether portal-based ACP tools increase the quality and quantity of ACP conversations and documentation that is available to inform medical decision-making.

Design and Implementation of Patient Portal-Based Advance Care Planning Tools

BACKGROUND

Electronic health record-based portal tools may help patients engage in advance care planning (ACP). We designed and implemented portal-based ACP tools to enable patients to create a medical durable power of attorney (MDPOA).

MEASURES

MDPOA documentation and System Usability Scale were assessed.

INTERVENTION

Stakeholder-informed portal-based ACP tools include an electronic MDPOA form, patient educational webpage, online messaging, and patient access to completed advance directives.

OUTCOMES

A total of 2814 patients used the tools over 15 months. Patients had a mean age 45 years (17-98 years) and 69% were women. Eighty-nine percent completed an MDPOA form, 2% called or sent online messages, and 8% viewed the MDPOA form but did not complete it. The tools were rated highly usable.

CONCLUSIONS/LESSONS LEARNED

Patients demonstrated willingness to use the portal to complete an MDPOA and rated the new ACP tools as highly usable. Future work will optimize population-based outreach strategies to engage patients in ACP through the portal.

Methotrexate pneumonitis in rheumatoid arthritis: increased prevalence with increasing latitude: an epidemiological study of trends in new zealand

BACKGROUND

There is an association between increasing prevalence and increasing latitude for some autoimmune diseases, including rheumatoid arthritis (RA). Furthermore, in RA patients, a geographical variation in methotrexate pneumonitis has been suggested at a regional level in New Zealand.

OBJECTIVE

The objective of the study was to determine if there is an increased incidence of methotrexate pneumonitis with increasing latitude in New Zealand.

METHODS

A search was conducted using the NZ Ministry of Health's National Minimum Data Set for patients with discharge codes for RA (M05, M06) or history of RA and drug-induced lung disease (J702, J703, J704) or other (J189, J680, J90, J984) and methotrexate (Y431), for the period July 1, 1999, to June 30, 2008. Anonymous data were provided by the Ministry of Health for the 43 patients fulfilling these coding criteria and also the latitude and population of each domicile code. A Poisson regression analysis was undertaken with latitude as a continuous variable, adjusting for the total population at different latitudes.

RESULTS

The incidence rate ratio for methotrexate pneumonitis shows a 16% increase per 1 degree of latitude (95% confidence interval, 7%-27%; P = 0.02).

CONCLUSIONS

There was a latitudinal gradient seen in the rate of patient discharges for methotrexate pneumonitis, in the defined period. This supports the hypothesis that there is a latitude-dependent risk factor for this disorder and raises questions regarding possible environmental cofactors. It also supports the growing pool of evidence that certain immune-mediated conditions are more common at higher latitudes.

Potent dipeptide inhibitors of the pp60c-src SH2 domain

The design, synthesis, and evaluation of dipeptide analogues as ligands for the pp60c-src SH2 domain are described. The critical binding interactions between Ac-Tyr-Glu-N(n-C5H11)2 (2) and the protein are established and form the basis for our structure-based drug design efforts. The effects of changes in both the C-terminal (11-27) and N-terminal (51-69) portions of the dipeptide are explored. Analogues with reduced overall charge (92-95) are also investigated. We demonstrate the feasibility of pairing structurally diverse subunits in a modest dipeptide framework with the goal of increasing the druglike attributes without sacrificing binding affinity.

The formation of a covalent complex between a dipeptide ligand and the src SH2 domain

The X-ray crystal structure of the src SH2 domain revealed the presence of a thiol residue (Cys 188) located proximal to the phosphotyrosine portion of a dipeptide ligand. An aldehyde bearing ligand (1) was designed to position an electrophilic carbonyl group in the vicinity of the thiol. X-ray crystallographic and NMR examination of the complex formed between (1) and the src SH2 domain revealed a hemithioacetal formed by addition of the thiol to the aldehyde group with an additional stabilizing hydrogen bond between the acetal hydroxyl and a backbone carbonyl.

Peptide ligands of pp60(c-src) SH2 domains: a thermodynamic and structural study

Thermodynamic measurements, structural determinations, and molecular computations were applied to a series of peptide ligands of the pp60(c-src) SH2 domain in an attempt to understand the critical binding determinants for this class of molecules. Isothermal titration calorimetry (ITC) measurements were combined with structural data derived from X-ray crystallographic studies on 12 peptide-SH2 domain complexes. The peptide ligands studied fall into two general classes: (1) dipeptides of the general framework N-acetylphosphotyrosine (or phosphotyrosine replacement)-Glu or methionine (or S-methylcysteine)-X, where X represents a hydrophobic amine, and (2) tetra- or pentapeptides of the general framework N-acetylphosphotyrosine-Glu-Glu-Ile-X, where X represents either Glu, Gln, or NH2. Dipeptide analogs which featured X as either hexanolamine or heptanolamine were able to pick up new hydrogen bonds involving their hydroxyl groups within a predominantly lipophilic surface cavity. However, due to internal strain as well as the solvent accessibility of the new hydrogen bonds formed, no net increase in binding affinity was observed. Phosphatase-resistant benzylmalonate and alpha,alpha-difluorobenzyl phosphonate analogs of phosphotyrosine retained some binding affinity for the pp60(c-src) SH2 domain but caused local structural perturbations in the phosphotyrosine-binding site. In the case where a reversible covalent thiohemiacetal was formed between a formylated phosphotyrosine analog and the thiol side chain of Cys-188, deltaS was 25.6 cal/(mol K) lower than for the nonformylated phosphotyrosine parent. Normal mode calculations show that the dramatic decrease in entropy observed for the covalent thiohemiacetal complex is due to the inability of the phosphotyrosine moiety to transform lost rotational and translational degrees of freedom into new vibrational modes.

A nucleic acid triple helix formed by a peptide nucleic acid-DNA complex

The crystal structure of a nucleic acid triplex reveals a helix, designated P-form, that differs from previously reported nucleic acid structures. The triplex consists of one polypurine DNA strand complexed to a polypyrimidine hairpin peptide nucleic acid (PNA) and was successfully designed to promote Watson-Crick and Hoogsteen base pairing. The P-form helix is underwound, with a base tilt similar to B-form DNA. The bases are displaced from the helix axis even more than in A-form DNA. Hydrogen bonds between the DNA backbone and the Hoogsteen PNA backbone explain the observation that polypyrimidine PNA sequences form highly stable 2:1 PNA-DNA complexes. This structure expands the number of known stable helical forms that nucleic acids can adopt.

Crystal structures of recombinant 19-kDa human fibroblast collagenase complexed to itself

Collagenase is a member of the matrix metalloproteinase (MMP) family of enzymes. Aberrant regulation of this family has been implicated in pathologies such as arthritis and metastasis. Two crystal forms of the catalytic (19-kDa) domain of human fibroblast collagenase have been determined using collagenase complexed with a peptide-based inhibitor (CPLX) as a starting model [Lovejoy et al. (1994) Science 263, 375]. The first crystal form (CF1) contains one molecule in the asymmetric unit and has been determined at 1.9-A resolution with an R factor of 19.8%. The second crystal form (CF2) contains two molecules (A and B) in the asymmetric unit and has been determined at 2.1-A resolution with an R factor of 19.7%. The catalytic domain of collagenase is spherical with an active site cleft that contains a ligated catalytic zinc ion. Collagenase shares some structural homology with the bacterial zinc proteinase, thermolysin [Matthews et al. (1972) Nature, New Biol. 238, 37], and the crayfish digestive peptidase, astacin [Bode et al. (1992) Nature 358, 164]. The amino terminus (Leu 102 to Gly 105) of CF1 and CF2 molecules A and B differs from the conformation found in CPLX by bending away from the molecule and interacting with the active site cleft of symmetry-related molecules. In this alternative conformation, both the mainchain nitrogen and carbonyl oxygen of Leu 102 ligate the symmetry-related catalytic zinc. Although there are structural differences in the active site clefts of CF1, CF2, and CPLX, a number of complex-stabilizing interactions are conserved. The structure of collagenase will be useful for developing compounds that selectively inhibit individual members of the closely related matrix metalloproteinase family.

Preliminary X-ray diffraction studies of recombinant 19 kDa human fibroblast collagenase

Crystals of the catalytic domain of human fibroblast collagenase have been grown in the presence and absence of an inhibitor. Crystals of the inhibitor complex grew from 0.2 M ammonium sulfate and 15 to 30% PEG 8000 at 22 degrees C as bipyramids in the space group P6(2) or P6(4). Crystals of the unligated enzyme grew as rods in the space group P4(1)2(1)2 or P4(3)2(1)2 from 1.0 to 2.0 M sodium formate at 4 degrees C. Both crystal forms grew quite slowly over a period of months, but ultimately yielded crystals that diffracted beyond 2.5 A. The collagenase samples used in these studies were heterogeneous at the amino terminus. Three major species (full length, N-1 and N-2) were identified by mass spectrometry and Edman sequencing. Analysis of dissolved crystals revealed the native crystal form selectively crystallized as the N-2 species; however, no selectivity of N-terminal forms was observed for crystals of the inhibitor complex.

A novel dimer configuration revealed by the crystal structure at 2.4 A resolution of human interleukin-5

Interleukin-5 (IL-5) is a lineage-specific cytokine for eosinophilpoiesis and plays an important part in diseases associated with increased eosinophils, such as asthma. Human IL-5 is a disulphide-linked homodimer with 115 amino-acid residues in each chain. The crystal structure at 2.4 A resolution reveals a novel two-domain structure, with each domain showing a striking similarity to the cytokine fold found in granulocyte macrophage and macrophage colony-stimulating factors, IL-2 (ref. 5), IL-4 (ref. 6), and human and porcine growth hormones. IL-5 is unique in that each domain requires the participation of two chains. The IL-5 structure consists of two left-handed bundles of four helices laid end to end and two short beta-sheets on opposite sides of the molecule. Surprisingly, the C-terminal strand and helix of one chain complete a bundle of four helices and a beta-sheet with the N-terminal three helices and one strand of the other chain. The structure of IL-5 provides a molecular basis for the design of antagonists and agonists that would delineate receptor recognition determinants critical in signal transduction. This structure determination extends the family of the cytokine bundle of four helices and emphasizes its fundamental significance and versatility in recognizing its receptor.

Purification, characterisation and crystallisation of selenomethionyl recombinant human interleukin-5 from Escherichia coli

Interleukin-5 (IL-5) plays a key role in the proliferation and differentiation of eosinophils. To aid the solution of the crystallographic three-dimensional structure, we have expressed large quantities of recombinant human IL-5 (hIL-5) in a methionine auxotroph strain of Escherichia coli (DL41) grown on an enriched seleno-DL-methionine-containing medium. Cell densities of A650 = 10 have been achieved. The selenomethionyl-labelled hIL-5 (Se-hIL-5) has been purified and found to contain 3.6 selenium atoms/dimer, and 0.4 methionine residues/dimer. In a B-cell growth factor assay, the Se-hIL-5 is significantly more active than the non-labelled hIL-5. Electrospray mass spectrometry shows two major peaks, with relative molecular masses of 26,326 +/- 6 and 26,280 +/- 8 corresponding to the 4Se and 3Se/1S forms of hIL-5. Unlike the methionine-containing hIL-5, the N-terminal selenomethionine is neither oxidised nor carbamoylated and can only be resolved into two species in isoelectric focusing gel electrophoresis. Se-hIL-5 crystallises in the same space group and unit cell as hIL-5. Difference Fourier calculations identify two of the selenomethionines corresponding to Met107 in the dimer. However, the N-terminal is disordered in the crystal, and the N-terminal selenomethionines are not resolved in the difference Fourier.

Crystallization and preliminary X-ray diffraction studies of recombinant human interleukin-5

Recombinant human interleukin-5 (rhIL-5) has been crystallized by the hanging drop vapor diffusion method using 0.1 M-Tris.HCl buffer (pH 8.5) containing 0.2 to 0.25 M-sodium acetate and 26 to 30% PEG 4000 at 22 degrees C. The parallel-piped crystals belong to the space group C2 with unit cell dimensions of a = 122.1 A, b = 36.11 A, c = 56.42 A, beta = 98.59 degrees. They diffract to at least 2.0 A resolution on a rotating anode X-ray source. The molecular mass weight of the protein and the volume of the unit cell suggest that the asymmetric unit contains one intermolecular disulfide-bonded homodimer.

Design and synthesis of novel 6,7-imidazotetrahydroquinoline inhibitors of thymidylate synthase using iterative protein crystal structure analysis

Antifolate inhibitors of thymidylate synthase (TS) have primarily been based on the structure of folic acid. This paper describes the identification and development of novel 6,7-imidazotetrahydroquinoline TS inhibitors by iterative ligand design, synthesis, and crystallographic analysis of protein-inhibitor complexes. Beginning with a high-resolution crystal structure of E. coli TS (TS, EC 2.1.1.45), an imidazotetrahydroquinoline inhibitor was designed de novo to occupy the folate binding pocket. Structural modifications of the initial compound 1h (Ki approximately 5 microM human/E. coli TS) were then made on the basis of feedback from additional cocrystal structures and activity data. An amino group in the 2-position of the imidazole was found to increase the potency of the series by 1-2 orders of magnitude. Other substitutions on the imidazole ring (1-CH3, 2-CH3, 2-NHCH3, 2-SCH3) generally led to weaker inhibition. Additional improvements in activity were obtained by modification of the substituents on the tetrahydroquinoline nitrogen, bringing the Ki of three of the compounds below 15 nM against the human TS enzyme. The compounds were tested for cytotoxicity and were shown to inhibit the growth of three tumor cell lines in vitro.

Crystal structure of the ribonuclease H domain of HIV-1 reverse transcriptase

The crystal structure of the ribonuclease (RNase) H domain of HIV-1 reverse transcriptase (RT) has been determined at a resolution of 2.4 A and refined to a crystallographic R factor of 0.20. The protein folds into a five-stranded mixed beta sheet flanked by an asymmetric distribution of four alpha helices. Two divalent metal cations bind in the active site surrounded by a cluster of four conserved acidic amino acid residues. The overall structure is similar in most respects to the RNase H from Escherichia coli. Structural features characteristic of the retroviral protein suggest how it may interface with the DNA polymerase domain of p66 in the mature RT heterodimer. These features also offer insights into why the isolated RNase H domain is catalytically inactive but when combined in vitro with the isolated p51 domain of RT RNase H activity can be reconstituted. Surprisingly, the peptide bond cleaved by HIV-1 protease near the polymerase-RNase H junction of p66 is completely inaccessible to solvent in the structure reported here. This suggests that the homodimeric p66-p66 precursor of mature RT is asymmetric with one of the two RNase H domains at least partially unfolded.

Conserved residues make similar contacts in two repressor-operator complexes

Comparison of a lambda repressor-operator complex and a 434 repressor-operator complex reveals that three conserved residues in the helix-turn-helix (HTH) region make similar contacts in each of the crystallographically determined structures. These conserved residues and their interactions with phosphodiester oxygens help establish a frame of reference within which other HTH residues make contacts that are critical for site-specific recognition. Such "positioning contacts" may be important conserved features within families of HTH proteins. In contrast, the structural comparisons appear to rule out any simple "recognition code" at the level of detailed side chain-base pair interactions.

Structure of the lambda complex at 2.5 A resolution: details of the repressor-operator interactions

The crystal structure of a complex containing the DNA-binding domain of lambda repressor and a lambda operator site was determined at 2.5 A resolution and refined to a crystallographic R factor of 24.2 percent. The complex is stabilized by an extensive network of hydrogen bonds between the protein and the sugar-phosphate backbone. Several side chains form hydrogen bonds with sites in the major groove, and hydrophobic contacts also contribute to the specificity of binding. The overall arrangement of the complex is quite similar to that predicted from earlier modeling studies, which fit the protein dimer against linear B-form DNA. However, the cocrystal structure reveals important side chain-side chain interactions that were not predicted from the modeling or from previous genetic and biochemical studies.

Systematic variation in DNA length yields highly ordered repressor-operator cocrystals

Crystals have been grown that contain the operator-binding domain of the lambda repressor and the lambda operator site OL1. Crystallization conditions were tested with a set of DNA fragments, ranging in length from 17 to 23 base pairs. The best crystals were grown with a 20-base pair DNA fragment. These crystals have space-group symmetry P2I, with unit cell dimensions a = 37.1 A, b = 68.8 A, c = 56.8 A, and a beta angle of 91.5 degrees. They diffracted to at least 2.5 A resolution. High resolution data from these crystals should allow the direct determination of how a repressor recognizes its operator site.

Crystallization of the Arc repressor

Arc, a repressor from Salmonella phage P22 has been crystallized from ammonium phosphate at pH 8.0. The crystals form in space group P212121 with a = 90.26 A, b = 52.88 A and c = 47.58 A. The crystals diffract to 2.2 A resolution.

Systematic analysis of possible hydrogen bonds between amino acid side chains and B-form DNA

The ways in which amino acid side chains could make a pair of hydrogen bonds within the major groove of B DNA are systematically analyzed. Hydrogen bond donors within the major groove are characterized by determining the idealized position of the hydrogen bond acceptors that they might bond with. It appears that an amino acid side chain could, at most, contact a pair of base pairs. The ten possible pairs of base pairs are analyzed to determine how they could be recognized by the amino acid side chains.

Structural convergence during protein evolution

Several recent protein crystallographic structure determinations have demonstrated the existence of considerable tertiary structural similarity among proteins otherwise having little similarity in either amino acid sequence or biological function. In order to assess the possibility that such proteins may have arisen through processes of divergent evolution from a common ancestor, a graphical presentation is given which correlates the pattern of allowed single base substitutions defined by the genetic code with the associated changes in the structural properties of the encoded amino acids. The results show that while a large degree of structural conservation is evident due to codon synonomy, there is, in general, little tendency for the code to be structurally conservative in the majority of the cases where codon single-base changes result in amino acid substitutions. The possible consequences of this pattern of potential amino acid substitutions are discussed in relation to protein evolutionary processes.