[Practical skills training : How suitable is Peyton's four-step approach for residents in urology?] / Vermittlung praktischer Fertigkeiten : Wie geeignet ist Peytons Vier-Schritte-Ansatz für urologische WeiterbildungsassistentInnen?

INTRODUCTION: The aim of residency is to acquire medical skills and abilities. One didactic model is "Peyton's four-step approach". The aim of the present study was to develop and evaluate a modified Peytonian approach for group interactions. The aim was to develop a course for the acquisition of practical skills and training assistants in suture techniques for urology. METHODS: A prospective study was conducted with a total of 38 participants and 6 tutors. In a modified four-step Peytonian approach, various suturing and knotting techniques were taught in a structured manner. Tutors evaluated the procedural activity using observation sheets. In addition, the learning method was evaluated by the participants and the tutors at the end of the course. In order to check the long-term learning success, a renewed survey of the participants was conducted after 6 months. RESULTS: 80% of the participants rated the modified teaching method as useful and 83% of the tutors rated the procedural implementation as good. Fluid movement sequences were difficult independent of the technique taught. After 6 months, the participants significantly improved their procedural skills in all techniques that were taught. CONCLUSION: This paper defines a four-step Peyton-based approach to teaching practical skills such as suturing and knotting used in urological training. The modified teaching method improved practical skills used in urology. This method should be considered in continuing education to promote self-confidence and increase the competence in surgical skills.

Clinical characteristics and outcomes of witnessed hypothermic cardiac arrest: A systematic review on rescue collapse.

AIMS: Cardiac arrest related to accidental hypothermia may occur at temperatures below 32 °C. Our goal was to describe the clinical characteristics and outcomes of patients who suffered from witnessed hypothermic cardiac arrest (CA) and assess the occurrence of hypothermic CA as a function of patient body temperature. METHODS: We conducted a systematic review of the literature on cases of hypothermic CA due to rescue collapse. Patient information data from hypothermic CA patients were collected and combined with additional unpublished data to assess the clinical characteristics and outcome of hypothermic CA patients. RESULTS: A total of 214 patients was included in this systematic review. Of the 206 witnessed hypothermic CA patients with a recorded body temperature, the average body temperature was 23.9 ± 2.7 °C with five patients (2.4%) having a core body temperature of >28 °C. The highest temperature of a patient surviving hypothermic witnessed cardiac arrest without other associated risk factors for cardiac arrest was 29.4 °C. The first recorded cardiac rhythm was asystole in 33 of the 112 patients (30%) for whom this information was available. The survival rate at hospital discharge of these hypothermic cardiac arrest patients was 73% (153 of 210 patients) and most survivors had favourable neurological outcome (89%; 102 of 105 patients). CONCLUSIONS: CA that is solely caused by hypothermia did not occurs for patients with a body temperature >30 °C. Our findings provide valuable new information that can be incorporated into the international clinical management guidelines of accidental hypothermia.

New engineered phenolic biosensors based on the AraC regulatory protein.

Customized transcription factors that control gene expression in response to small molecules can act as endogenous molecular biosensors and are valuable tools for synthetic biology. We previously engineered the Escherichia coli regulatory protein AraC to respond to non-native inducers such as D-arabinose and triacetic acid lactone. Those prior studies involved the construction and screening of individual 4- or 5-site saturation mutagenesis libraries, followed by iterative rounds of positive- and negative fluorescence-activated cell sorting (FACS). Here we describe an improved screening platform and the isolation of several new and potentially useful AraC variants that respond to vanillin and salicylic acid. To increase throughput and reduce total screening time, selection steps were added to the sorting workflow. Two different site-saturation libraries and a random mutagenesis library were pooled together and >108 variants were subjected to iterative FACS and selection in search of variants responding to a panel of compounds. The new phenolic-sensing variants show responses >100-fold over background and are highly specific towards their target compound. The isolation of these variants further demonstrates the potential for engineering the AraC transcriptional regulatory protein for molecular sensing and reporting, and our improved screening system should prove effective in designing similar biosensors.

Predictors of community-associated Staphylococcus aureus, methicillin-resistant and methicillin-susceptible Staphylococcus aureus skin and soft tissue infections in primary-care settings.

Skin and soft tissue infections (SSTIs) due to Staphylococcus aureus have become increasingly common in the outpatient setting; however, risk factors for differentiating methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) SSTIs are needed to better inform antibiotic treatment decisions. We performed a case-case-control study within 14 primary-care clinics in South Texas from 2007 to 2015. Overall, 325 patients [S. aureus SSTI cases (case group 1, n = 175); MRSA SSTI cases (case group 2, n = 115); MSSA SSTI cases (case group 3, n = 60); uninfected control group (control, n = 150)] were evaluated. Each case group was compared to the control group, and then qualitatively contrasted to identify unique risk factors associated with S. aureus, MRSA, and MSSA SSTIs. Overall, prior SSTIs [adjusted odds ratio (aOR) 7·60, 95% confidence interval (CI) 3·31-17·45], male gender (aOR 1·74, 95% CI 1·06-2·85), and absence of healthcare occupation status (aOR 0·14, 95% CI 0·03-0·68) were independently associated with S. aureus SSTIs. The only unique risk factor for community-associated (CA)-MRSA SSTIs was a high body weight (⩾110 kg) (aOR 2·03, 95% CI 1·01-4·09).

Risk factors for methicillin-resistant Staphylococcus aureus skin and soft tissue infection in MRSA-colonized patients discharged from a Veterans Affairs hospital.

Currently, limited studies have quantified the risk of methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections (SSTIs) for MRSA-colonized patients on discharge from hospital. Our retrospective, case-control study identified independent risk factors for the development of MRSA SSTIs among such patients detected by active MRSA nasal screening in an acute care hospital by PCR on admission, and bacteriological cultures on discharge. Cases were MRSA-colonized patients aged ⩾18 years who developed a MRSA SSTI post-discharge and controls were those who did not develop a MRSA SSTI post-discharge. Controls were matched to cases by length of follow-up (±10 days) for up to 18 months. Potential demographic and clinical risk factors for MRSA infection were identified using electronic queries and manual chart abstraction; data were compared by standard statistical tests and variables with P values ⩽0·05 in bivariable analysis were entered into a logistic regression model. Multivariable analysis demonstrated prior hospital admission within 12 months (P = 0·02), prior MRSA infection (P = 0·05), and previous myocardial infarction (P = 0·01) were independently predictive of a MRSA SSTI post-discharge. Identification of MRSA colonization upon admission and recognition of risk factors could help identify a high-risk population that could benefit from MRSA SSTI prevention strategies.

Impact of empiric weight-based vancomycin dosing on nephrotoxicity and mortality in geriatric patients with methicillin-resistant Staphylococcus aureus bacteraemia.

WHAT IS KNOWN AND OBJECTIVE: Few studies have evaluated the effect of vancomycin dosing on the health outcomes in geriatric patients. Data are needed to determine whether higher vancomycin dosing strategies are more effective in geriatric patients and/or lead to excessive rates of adverse events. METHODS: This study used a subset of patients aged ≥65 years from a multicentre, retrospective, cohort study of methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia. Patients received ≥ 48 h of empiric vancomycin between 1 July 2002 and 30 June 2008. We compared the incidence of nephrotoxicity and in-hospital mortality in patients who received guideline-recommended dosing (at least 15 mg/kg/dose) to patients who received lower dosing. Multivariable generalized mixed-effect models were constructed to determine independent risk factors for nephrotoxicity and in-hospital mortality. RESULTS AND DISCUSSION: Half of the cohort (46% of 92 patients) received guideline-recommended dosing. Empiric use of weight-based dosing did increase the percentage of patients achieving a vancomycin trough ≥ 15 mg/L (57% vs. 42%). Nephrotoxicity occurred in 32% of patients and 26% died during their hospitalization. Guideline-recommended dosing was not associated with significant changes in nephrotoxicity (OR 1·13; 95% CI 0·40-3·19) or in-hospital mortality (OR 1·14; 95% CI 0·41-3·18) in the multivariable analysis. WHAT IS NEW AND CONCLUSION: In this study of geriatric patients, guideline-recommended dosing was not associated with significant changes in nephrotoxicity or mortality. As 40% of the patients who received guideline-recommended dosing failed to achieve a target vancomycin trough of ≥ 15 mg/L, future studies should focus on dosing strategies to increase target attainment rate.

Performance of the LHCb RICH detector at the LHC.

The LHCb experiment has been taking data at the Large Hadron Collider (LHC) at CERN since the end of 2009. One of its key detector components is the Ring-Imaging Cherenkov (RICH) system. This provides charged particle identification over a wide momentum range, from 2-100 GeV/c. The operation and control, software, and online monitoring of the RICH system are described. The particle identification performance is presented, as measured using data from the LHC. Excellent separation of hadronic particle types (π, K, p) is achieved.

Guideline-concordant therapy and outcomes in healthcare-associated pneumonia.

Healthcare-associated pneumonia (HCAP) guidelines were first proposed in 2005 but have not yet been validated. The objective of this study was to compare 30-day mortality in HCAP patients treated with either guideline-concordant (GC)-HCAP therapy or GC community-acquired pneumonia (CAP) therapy. We performed a population-based cohort study of >150 hospitals in the US Veterans Health Administration. Patients were included if they had one or more HCAP risk factors and received antibiotic therapy within 48 h of admission. Critically ill patients were excluded. Independent risk factors for 30-day mortality were determined in a generalised linear mixed-effect model, with admitting hospital as a random effect. Propensity scores for the probability of receiving GC-HCAP therapy were calculated and incorporated into a second logistic regression model. A total of 15,071 patients met study criteria and received GC-HCAP therapy (8.0%), GC-CAP therapy (75.7%) or non-GC therapy (16.3%). The strongest predictors of 30-day mortality were recent hospital admission (OR 2.49, 95% CI 2.12-2.94) and GC-HCAP therapy (OR 2.18, 95% CI 1.86-2.55). GC-HCAP therapy remained an independent risk factor for 30-day mortality (OR 2.12, 95% CI 1.82-2.48) in the propensity score analysis. In nonsevere HCAP patients, GC-HCAP therapy is not associated with improved survival compared with GC-CAP therapy.

Immunogenicity of SEREX-identified antigens and disease outcome in pancreatic cancer.

Despite spontaneous or vaccination-induced immune responses, pancreatic cancer remains one of the most deadly immunotherapy-resistant malignancies. We sought to comprehend the spectrum of pancreatic tumor-associated antigens (pTAAs) and to assess the clinical relevance of their immunogenicity. An autologous SEREX-based screening of a cDNA library constructed from a pancreatic T3N0M0/GIII specimen belonging to a long-term survivor (36 months) revealed 18 immunogenic pTAA. RT-PCR analysis displayed broad distribution of the identified antigens among normal human tissues. PNLIPRP2 and MIA demonstrated the most distinct pancreatic cancer-specific patterns. ELISA-based screening of sera for corresponding autoantibodies revealed that although significantly increased, the immunogenicity of these molecules was not a common feature in pancreatic cancer. QRT-PCR and immunohistochemistry characterized PNLIPRP2 as a robust acinar cell-specific marker whose decreased expression mirrored the disappearance of parenchyma in the diseased organ, but was not related to the presence of PNLIPRP2 autoantibodies. Analyses of MIA-known to be preferentially expressed in malignant cells-surprisingly revealed an inverse correlation between intratumoral gene expression and the emergence of autoantibodies. MIA(high) patients were autoantibody-negative and had shorter median survival when compared with autoantibody-positive MIA(low) patients (12 vs. 34 months). The observed pTAA spectrum comprised molecules associated with acinar, stromal and malignant structures, thus presenting novel targets for tumor cell-specific therapies as well as for approaches based on the bystander effects. Applying the concept of cancer immunoediting to interpret relationships between gene expression, antitumor immune responses, and clinical outcome might better discriminate between past and ongoing immune responses, consequently enabling prognostic stratification of patients and individual adjustment of immunotherapy.

Medical resource utilization among community-acquired pneumonia patients initially treated with levofloxacin 750 mg daily versus ceftriaxone 1000 mg plus azithromycin 500 mg daily: a US-based study.

OBJECTIVE: The 2007 American Thoracic Society/Infectious Diseases Society of America (ATS/IDSA) guidelines recommend that community-acquired pneumonia (CAP) patients admitted to hospital wards initially receive respiratory fluoroquinolone monotherapy or beta-lactam plus macrolide combination therapy. There is little evidence as to which regimen is preferred, or if differences in medical resource utilization exist between therapies. Thus, the authors compared length of hospital stay (LOS) and length of intravenous antibiotic therapy (LOIV) for patients who received initial levofloxacin 750 mg daily versus ceftriaxone 1000 mg plus azithromycin 500 mg daily ('combination therapy'). RESEARCH DESIGN AND METHODS: Adult hospital CAP cases from January 2005 to December 2007 were identified by principal discharge diagnosis code. Patients with a chest infiltrate and medical notes indicative of CAP were included. Direct intensive care unit admits and healthcare-associated cases were excluded. A propensity score technique was used to balance characteristics associated with initial antimicrobial therapy using multivariable regression to derive the scores. Propensity score categories, defined as propensity score quintiles, rather than propensity scores themselves, were used in the least squares regression model to assess the impact of LOS and LOIV. RESULTS: A total of 495 patients from six hospitals met study criteria. Of these, 313 (63%) received levofloxacin and 182 (37%) received combination therapy. Groups were similar with respect to age, sex, most comorbidities, presenting signs and symptoms, and Pneumonia Severity Index (PSI) risk class. Patients on combination therapy were more likely to have heart failure and receive pre-admission antibiotics. Adjusted least squares mean (+/-SE) LOS and LOIV were shorter with levofloxacin versus combination therapy: LOS, 4.6 +/- 0.17 vs. 5.4 +/- 0.22 days, p < 0.01; and LOIV, 3.6 +/- 0.17 vs. 4.8 +/- 0.21 days, p < 0.01. Results for PSI risk class III or IV patients were: LOS, 5.0 +/- 0.30 vs. 5.9 +/- 0.37 days, p = 0.07; and LOIV, 3.7 +/- 0.33 vs. 5.2 +/- 0.39 days, p < 0.01. Due to the retrospective study design, limited sample size, and scope (single health-network), the authors encourage replication of this study in other data sources. CONCLUSIONS: Given the LOS and LOIV reductions of 0.8 and 1.2 days, respectively, utilization of levofloxacin 750 mg daily for CAP patients admitted to the medical floor has the potential to result in substantial cost savings for US hospitals.

Oral ganciclovir versus valganciclovir for cytomegalovirus prophylaxis in high-risk liver transplant recipients.

This retrospective review compared oral valganciclovir (VGCV) 450 mg daily for 6 months versus oral ganciclovir (GCV) 1000 mg 3 times daily for 3 months in preventing cytomegalovirus (CMV) disease in high-risk liver transplant recipients.We evaluated all CMV donor positive-recipient negative liver transplant recipients managed at University Health System in San Antonio,Texas from August 1996 to September 2006. CMV disease was confirmed by polymerase chain-reaction or antigenemia assay, and CMV invasive disease by tissue biopsy. Patient demographics, laboratory results, complications, and therapies were collected via retrospective chart review. Patients < 18 years of age or those who died during transplant admission were excluded. Primary endpoints included incidence, onset, and severity of CMV disease up to 1 year post transplant. Data collection also included patient demographics, immunosuppression, CMV treatment regimens, and relevant lab results. A total of 64 patients (43 VGCV and 21 GCV) were identified. Four patients developed CMV disease:VGCV (3/43,7%) versus GCV (1/21, 5%) (P=1.0), with 1 VGCV patient experiencing tissue-invasive CMV. In all cases, onset of CMV disease occurred after prophylaxis was discontinued. Onset occurred at 24, 27, and 45 weeks post transplant in the VGCVgroup, and at 26 weeks in the 1 patient on GCV. Four patients received rabbit antithymocyte globulin (rATG) induction; 1 patient received rATG and developed CMV disease, with no statistical difference compared with the 3 remaining patients who received rATG but did not develop CMV disease (P=0.09). No difference was found in incidence of CMV disease between patients who received GCV and those who received VGCV at our institution.

Monotherapy versus combination antibiotic therapy for patients with bacteremic Streptococcus pneumoniae community-acquired pneumonia.

The purpose of this study was to examine the impact of antimicrobial monotherapy vs combination therapy on length of stay and mortality for patients with Streptococcus pneumoniae pneumonia. Thirty-nine percent of patients received monotherapy, while 61% received combination therapy. Although there was no significant difference in mortality (OR 1.25, 95% CI = 0.25-6.8), there was a significant increase in length of stay for patients who received combination therapy (p = 0.02). Patients with bacteremic pneumococcal pneumonia treated with empiric combination therapy had no significant difference in mortality; however, they did have increased length of stay after adjusting for severity of illness. Randomized controlled trials are needed to determine what is the optimal empiric antimicrobial regime for patients with community-acquired pneumonia.

The contribution of pharmacokinetic-pharmacodynamic modelling with Monte Carlo simulation to the development of susceptibility breakpoints for Neisseria meningitidis.

This study used pharmacokinetic-pharmacodynamic (PK-PD) modelling and MICs of 15 antimicrobial agents, derived from testing a large international culture collection, to assist in the development of interpretative criteria, i.e., breakpoints, for Neisseria meningitidis. PK parameters, protein binding, percentage penetration into cerebrospinal fluid (CSF), and the variability of these values, were extracted from the published literature for the 15 agents. PK-PD parameters have not been developed specifically for N. meningitidis in animal or human studies. Thus, it was necessary to invoke PK-PD targets from other organisms that cause infections at similar sites. The PK-PD targets utilised were: time above the MIC for at least 50% of the dosing interval for all beta-lactams, chloramphenicol, sulphafurazole and trimethoprim-sulphamethoxazole; an AUC/MIC ratio of >or=25 for the tetracyclines and macrolides; and an AUC/MIC ratio of >or=125 for the fluoroquinolones. A 10 000-subject Monte Carlo simulation was designed with the usual dosing regimens of each antimicrobial agent at MIC values of 0.03-64 mg/L in both serum and CSF. The PK-PD breakpoint was defined as the MIC at which the calculated target attainment was >or=95%. Using these assumptions, the proposed PK-PD breakpoints were: azithromycin, 0.125 mg/L; doxycycline, 0.25 mg/L; cefotaxime, ciprofloxacin and levofloxacin, 0.5 mg/L; penicillin G, meropenem, rifampicin, tetracycline and minocycline, 1 mg/L; chloramphenicol and sulphafurazole, 2 mg/L; and ampicillin, ceftriaxone and trimethoprim-sulphamethoxazole, 4 mg/L. Proposed PK-PD breakpoints applicable to CSF were: penicillin and cefotaxime, 0.06 mg/L; rifampicin, 0.125 mg/L; ceftriaxone, meropenem and trimethoprim-sulphamethoxazole, 0.25 mg/L; ampicillin, 0.5 mg/L; and chloramphenicol, 1 mg/L.

[Investigation about the clinical use of brushite- and hydroxylapatite-cement in sheep]. / Untersuchungen uber den klinischen Einsatz von Brushite- und Hydroxylapatit-Zement beim Schaf.

For future clinical use as synthetic bone replacement, an injectable brushite-(chronOS-Inject) and hydroxylapatite-(Biobon) cement were compared in a drill hole model in 10 sheep over time at 2, 4, 6, 8, 16 and 24 weeks. Results were compared regarding their practical use, biocompatibiliy, resorption mechanism and subsequent new bone formation. The cements were filled into drill holes (psi 8 x 13mm) of the proximal and distal humerus, and femur and the samples evaluated macroscopically, radiologically and microscopically including histomorphometrical quantification of percentages of new bone, fibrous tissue and remnants of cements. The cement area decreased continuously from 2 to 24 weeks with chronOS-Inject, as well as the area of granules. Inversely, the subsequent new bone formation increased from 2-24 weeks accordingly. With Biobon the cement area decreased slower between 2 and 24 weeks, and the new bone formation was less. Both cements were well integrated into the bone in long bones. chronOS-Inject demonstrated good biocompatibility and was almost completely replaced through bone within 24 weeks. Biobon was resorbed considerably slower and initially a slight inflammatory reaction including bone resorption was observed within the adjacent host bone.

Continuous infusion beta-lactams for intensive care unit pulmonary infections.

This study evaluated the pharmacodynamics of continuous infusion beta-lactams against pulmonary isolates of Gram-negative bacteria from patients managed in intensive care units (ICUs) in the USA. Multiple 10,000-patient Monte Carlo simulations were performed by integrating pharmacokinetic data from healthy individuals with 2408 MICs from the 2002 Intensive Care Unit Surveillance System database. These pharmacodynamic simulations suggested that continuous infusion regimens of cefepime, aztreonam, ceftazidime and piperacillin-tazobactam 13.5 g have the greatest likelihood of achieving pharmacodynamic targets against isolates of Enterobacteriaceae in the ICU. Beta-lactams are unlikely to achieve pharmacodynamic targets against Pseudomonas aeruginosa or Acinetobacter baumannii when administered as monotherapy.

Compositional changes of a dicalcium phosphate dihydrate cement after implantation in sheep.

A hydraulic calcium phosphate cement having dicalcium phosphate dihydrate (DCPD) as end-product of the setting reaction was implanted in a cylindrical defect in the diaphysis of sheep for up to 6 months. The composition of the cement was investigated as a function of time. After setting, the cement composition consisted essentially of a mixture of DCPD and beta-tricalcium phosphate (beta-TCP). In the first few weeks of implantation, the edges of the cement samples became depleted in DCPD, suggesting a selective dissolution of DCPD, possibly due to low pH conditions. The cement resorption at this stage was high. After 8 weeks, the resorption rate slowed down. Simultaneously, a change of the color and density of the cement center was observed. These changes were due to the conversion of DCPD into a poorly crystalline apatite. Precipitation started after 6-8 weeks and progressed rapidly. At 9 weeks, the colored central zone reached its maximal size. The fraction of beta-TCP in the cement was constant at all time. Therefore, this study demonstrates that the resorption rate of DCPD cement is more pronounced as long as DCPD is not transformed in vivo.

Calibration processes in desert ant navigation: vector courses and systematic search.

This study investigates the ability of desert ants to adapt their path integration system to an "open-jaw" training paradigm, in which the point of arrival (from the nest) does not coincide with the point of departure (to the nest). Upon departure the ants first run off their home vector and then start a systematic search for the nest. Even if they are subjected to this training-around-a-circuit procedure for more than 50 times in succession, they never adopt straight homeward courses towards the nest. Their path integration vector gets slightly recalibrated (pointing a bit closer to the nest), and their search pattern gets asymmetric (with its search density peak shifted towards the nest), but the bipartite structure of the inbound trajectory invariably remains. These results suggest (1). that the ants cannot learn separate inbound and outbound vectors (i.e. vectors that are not 180 degrees reversals of each other), (2). that the recalibrated vector is dominated by the ant's outbound course, (3). that the recalibration of the vector and the modification of the search geometry are fast and flexible processes occurring whenever the ant experiences a mismatch between the stored and actual states of its path integrator.

Modeling and closed-loop control of hypnosis by means of bispectral index (BIS) with isoflurane.

A model-based closed-loop control system is presented to regulate hypnosis with the volatile anesthetic isoflurane. Hypnosis is assessed by means of the bispectral index (BIS), a processed parameter derived from the electroencephalogram. Isoflurane is administered through a closed-circuit respiratory system. The model for control was identified on a population of 20 healthy volunteers. It consists of three parts: a model for the respiratory system, a pharmacokinetic model and a pharmacodynamic model to predict BIS at the effect compartment. A cascaded internal model controller is employed. The master controller compares the actual BIS and the reference value set by the anesthesiologist and provides expired isoflurane concentration references to the slave controller. The slave controller maneuvers the fresh gas anesthetic concentration entering the respiratory system. The controller is designed to adapt to different respiratory conditions. Anti-windup measures protect against performance degradation in the event of saturation of the input signal. Fault detection schemes in the controller cope with BIS and expired concentration measurement artifacts. The results of clinical studies on humans are presented.

Analysis of etoposide binding to subdomains of human DNA topoisomerase II alpha in the absence of DNA.

Epipodophyllotoxins are effective anti-tumor drugs that inhibit eukaryotic DNA topoisomerase II by trapping the enzyme in a covalent complex with DNA. We show that both the recombinant N-terminal ATPase domain and the B'A' core domain of human topoisomerase IIalpha (htopoIIalpha) bind radiolabeled etoposide specifically, even in the absence of DNA. The addition of ATP impairs etoposide binding to the holoenzyme and the N-terminal domain, but not to the core domain. To see if this interference resembles that between novobiocin and ATP in the bacterial GyrB subunit, we modeled the structure of the N-terminal domain of htopoIIalpha and performed molecular docking analysis with etoposide. Mutagenesis of critical amino acids, predicted to stabilize the drug within the N-terminal domain, reveals a less efficient binding of etoposide to the mutated proteins as monitored by direct drug binding assays, although the binding of ATP is not affected.