[Efficacy of dupilumab in real practice in the treatment of severe forms of asthma and atopic dermatitis (comparative retrospective study)].

BACKGROUND: Dupilumab, a fully human monoclonal antibody directed against the common α-subunit of interleukin (IL)-4 receptors and blocking signaling from both IL-4 and IL-13, may be recommended for the treatment of moderate to severe atopic dermatitis (AD) and bronchial asthma (BA). AIM: To perform a comparative assessment of the effectiveness of maintenance therapy with dupilumab in patients with severe BA as the main indication for genetically engineered biological drugs and in patients with severe asthma with concomitant severe AD as the indication for targeted therapy. MATERIALS AND METHODS: A 6-month retrospective comparative study was performed at the specialized reference center for allergology and immunology. The study included 115 adult patients of both sexes treated with dupilumab for uncontrolled severe asthma as the main indication for targeted therapy (BA group; n=65) or for a combination of severe uncontrolled asthma and severe AD (BAAD; n=50). Dupilumab was administered subcutaneously for 6 months. The first dose was 600 mg once and then 300 mg Q2W. Evaluation of the effectiveness of dupilumab therapy at 6 months of treatment in both groups included achieving asthma control (ACT, ACQ5), improving pulmonary function test, reducing the risk of exacerbations and the need for systemic glucocorticosteroids (SGCS), improving quality of life (AQLQ), change of biomarkers (FeNO, eosinophil count) and the course of comorbid diseases, including improvement in the AD (SCORAD, EASI) and rhinosinusitis polyposa (SNOT-22). RESULTS AND CONCLUSION: During dupilumab therapy, in a significant proportion of patients, regardless of the presence or absence of other T2-associated diseases (e.g., AD or rhinosinusitis polyposa), an improvement in asthma was demonstrated as early as in the first 6 months of treatment with dupilumab in all recommended domains for assessing the response to targeted therapy: improving asthma control and respiratory function, reducing the frequency of moderate and severe exacerbations associated with the use of SGCS and/or hospitalization, a positive effect on the quality of life and the comorbid diseases, as well as a cumulative reduction in the need for SGCS.

[Pre-exposure prophylaxis of new COVID-19 coronavirus infection with tixagevimab/cilgavimab in adult Moscow patients with primary immunodeficiencies].

BACKGROUND: Primary immunodeficiencies (PIDs), now known as inborn errors of immunity, are a group of inherited diseases caused by defects in the genes that control the immune response. Patients with PIDs have risks of developing a severe course and/or death in COVID-19. Passive immunization with long-acting monoclonal antibodies (MABs) to SARS-CoV-2 should be considered as pre-exposure prophylaxis in patients with PIDs. Tixagevimab/cilgavimab is a combination of MABs that bind to the SARS-CoV-2 spike protein. AIM: To evaluate the efficacy and safety of pre-exposure prophylaxis of new SARS-CoV-2 infection in PIDs with the combination of tixagevimab/cilgavimab. MATERIALS AND METHODS: Forty eight patients diagnosed with PIDs were included in the study. Median follow-up after drug administration was 174 days. The total number of confirmed coronavirus infections in patients with PIDs as well as 6 months before and after administration of MAT were assessed. RESULTS: In the analyzed cohort, the overall incidence of COVID-19 from pandemic onset to MABs administration was 75% (36/48), with 31% (11/36) of over-infected patients having had the infection more than once. The incidence of COVID-19 immediately 6 months before the introduction of tixagevimab/cilgavimab was 40%. All patients who had COVID-19 after pre-exposure prophylaxis had a mild infection. The incidence of COVID-19 6 months after tixagevimab/cilgavimab administration significantly decreased compared to the incidence 6 months before administration (7 and 40%, respectively; p<0.001). CONCLUSION: The use of tixagevimab/cilgavimab in patients with PIDs is effective as pre-exposure prophylaxis and reduces the risk of severe COVID-19.

[Analysis of predictors of response to anti-IgE therapy in patients with severe atopic bronchial asthma in real clinical practice].

INTRODUCTION: Guidelines on Biological Therapy for Bronchial Asthma of the European Academy of Allergy and Clinical Immunology (EAACI) identified a number of controversial issues for additional outcome analysis using randomized clinical trials and data from routine clinical practice. In particular, there is unmet need to clarify algorithms for prescribing biologicals using predictors of response and its timing, taking into account risk factors and multimorbidity. Omalizumab is a recombinant humanized monoclonal anti-IgE antibody of IgG1 class used for the treatment of severe refractory atopic bronchial asthma (BA) and a variety of IgE-mediated diseases. Among biological agents, this "pioneer molecule" has the greatest experience in the "allergology and immunology" profile. Detailed description of the "nonresponders" portraits will allow to perform the therapy response assessment on time and facilitate rational planning of individual therapy, which is a prerequisite for biologicals era. Using only routine methods, it is possible to perform initial and dynamic screening to phenotype a heterogeneous cohort of patients with severe asthma and chose the optimal strategy. AIM: To identify predictors of nonresponse to omalizumab anti-IgE therapy in patients with severe atopic BA and to establish optimal timing of efficacy assessment using retrospective analysis of data from the Biologic Therapy Registry of Allergology and Immunology in routine clinical practice. MATERIALS AND METHODS: A retrospective single-center registry study was conducted at the Allergy and Immunology Reference Center from June 2017 to August 2021. 135 patients with severe BA, with confirmed perennial sensitization, who received omalizumab according to the recommendations of the current version of GINA, were selected from the clinical and dynamic observational system (registry). Dosing regimen and administration frequency of omalizumab were determined in accordance with the instructions for the drug. Assessment of therapy efficacy was performed at the time point 4, 6 and 12 months. Patients were subgrouped into "responders" and "non-responders" according to the following criteria: ACT score less than 19 and/or difference between initial ACT score in dynamics less than 3 points; forced expiratory volume in the first second less than 80%; combination of these two criteria. Nonparametric methods of descriptive statistics were used in data processing: median, interquartile range. Differences were considered significant at p0.05. MannWhitney U-test, KruskalWallis one-way analysis of variance, and Fisher's 2 test were used to compare quantitative characteristics. RESULTS: Heterogeneous subgroups of patients differing in reaching the criteria of "non-responders" to treatment were identified; the informativity of modifiable and unmodifiable factors differed at time-points of dynamic observation. In the differential analysis, two profiles of "nonresponders" were defined in combination with the most significant predictors of "nonrsponse" to omalizumab. According to the data obtained, one of the clinical phenotypes, namely the combination of severe asthma with the Samters triad, corresponded to the characteristics of the patient "nonresponders": age of onset is about 30 years, females, severe exacerbations of BA while taking non-steroidal anti-inflammatory drugs, accompanied with high levels of eosinophilia. CONCLUSION: The data obtained illustrates the hypothesis of pathogenetic heterogeneity of severe BA with the phenomenon of overlapping phenotypes and can serve as an additional orienteer for creating the individual plan of anti-IgE therapy in real clinical practice.

[Levilimab and baricitinib prescribing experience in outpatient COVID-19 patients' treatment].

AIM: To study the effect of levilimab or baricitinib in combination with standard therapy (ST) on the incidence of severe viral pneumonia associated with a new coronavirus infection COVID-19. MATERIALS AND METHODS: A multicenter, open-label observational study of the efficacy and safety of levilimab in combination with ST (group 1, n=100), baricitinib in combination with ST (group 2, n=139), or in comparison with ST (group 3, n=200) in outpatients with verified CT-1 pneumonia. RESULTS: According to the results of laboratory tests, patients treated with levilimab in combination with ST had the best dynamics of changes in CRP from reliably the highest level (mg/L) to the lowest in comparison with other groups. In the group of patients with ST, in contrast to the other groups, no dynamics of CRP was observed by day 5 of therapy. In group of hospitalized patients initially receiving levilimab in addition to ST, the rate of transfer to the intensive care unit (2 patients, 9.52%) and length of stay (4 days) was significantly lower compared to the values in patients in both the baricitinib group in combination with ST (7 patients, 15.56%; 5 days [interquartile range 36.5]) and in patients receiving ST alone (7 patients, 15.56%; 5 days [interquartile range 36.5]). Also in hospitalized patients we observed no statistically significant intergroup differences in the incidence of infectious complications and thromboembolic events, which confirms the safety of including levilimab or baricitinib in COVID-19 pathogenetic therapy regimens. Observational results support the hypothesis that the initial inclusion of levilimab or baricitinib in addition to ST is accompanied by a reduced risk of viral pneumonia progression. CONCLUSION: The addition of levilimab or baricitinib to the therapy regimen for coronavirus infection during the outpatient phase has demonstrated a preemptive anti-inflammatory effect and reduced the probability of lung tissue damage progression.

[Efficacy and safety of regdanvimab in patients with mild/moderate COVID-19 and high risk of progression of the disease: a retrospective study in a short-term stay unit].

BACKGROUND: The use of virus-neutralizing monoclonal antibodies is an effective method of etiotropic therapy for SARS-CoV-2 in patients of high-risk groups of severe COVID-19. Regdanvimab is a single-component monoclonal antibodies immunoglobulin G1, whose mechanism of action is aimed at binding SARS-CoV-2 virus at the RBD site of the spike protein S1 domain. In the Russian Federation, regdanvimab is approved for emergency administration in COVID-19 for adult patients not requiring respiratory therapy who are at high risk of developing a severe course of the disease. AIM: To evaluate the efficacy and safety of therapy with regdanvimab in patients with mild/moderate COVID-19 in a short-term hospital unit. MATERIALS AND METHODS: Virus-neutralizing therapy with regdanvimab was performed at the short-term hospital unit of the Moscow City Clinic. An open retrospective observational single-center study included 92 adult patients with mild/moderate coronavirus infection. All patients had comorbid chronic diseases and belonged to the high-risk group for the development of a severe COVID-19. INCLUSION CRITERIA: age 18 to 75 years; presence of a verified diagnosis of COVID-19 of mild/moderate COVID-19, polymerase chain reaction (PCR) confirmed; one or more chronic diseases; first 7 days from the onset of the first symptoms of COVID-19 (including day 7). EXCLUSION CRITERIA: need for oxygen support. Clinical efficacy was assessed according to the World Health Organization Сlinical Progression Scale and supplemented with laboratory markers at baseline and in dynamics, as well as with monitoring of virus elimination by PCR. STATISTICS: Calculations were performed using the statistical computing environment R 4.1.3 (R Foundation for Statistical Computing, Austria). For quantitative indices the median (1; 3 quartiles) was indicated. For binomial signs we calculated 95% confidence intervals according to Wilson's method. Time interval analysis was performed according to the KaplanMeier method. The significance level was determined at p0.05. RESULTS: A significant decrease in the severity of clinical manifestations according to the World Health Organization Clinical Progression Scale was noted by patients by day 4 after regdanvimab administration. All 92 patients in the cohort were discharged from the hospital l on average on day 5 after regdanvimab administration and on day 9 of the disease. On day 4 after drug administration 82% of patients was being PCR negative. No adverse events related to the administration of regdanvimab were reported during the study. CONCLUSION: In real clinical practice, the efficacy and safety of regdanvimab in patients at high risk of severe COVID-19 was confirmed once again, with a positive clinical result observed in a mixed cohort by the causative agent omicron and delta strain.

Peculiarities of radioactive soil contamination in places of underground nuclear tests in the Semipalatinsk test site.

The article highlights the results of a radioecological survey of the surface areas of combat boreholes at the Sary-Uzen site located on the territory of the Semipalatinsk Test Site (STS), where underground nuclear tests in these boreholes were conducted earlier. The surface areas of boreholes were examined the levels of radioactive contamination of the soil were determined. A total of 2 main groups were identified. The first group includes boreholes with radioactive contamination of the soil on the surface area. The second group includes boreholes with no radioactive contamination of the surface soil layer. The first group can be divided into boreholes with a deformation of the ground surface and without it. For each variety, depending on the specifics of the nuclear test, the characteristic features of radioactive contamination were determined. Based on the results of the survey, the ranges of specific activity values were established.

[Criteria for the optimal use of interleukin-6 receptor blockers in patients with COVID-19].

AIM: To determine the criteria for the optimal use of IL-6 receptor blockers in patients with COVID-19 community-acquired pneumonia based on predictors of adverse outcomes. MATERIALS AND METHODS: The single-center, non-randomized prospective study included 190 patients with community-acquired pneumonia caused by coronavirus 2 between the beginning of March and the end of May 2020. Of these, 89 patients received tocilizumab and 101 patients received sarilumab. The study inclusion criterion for the patient was indications for initiating therapy with one of the inhibitors of IL-6 receptors (anti-IL-6R) according to the Interim guidelines (versions 4 and 5). The exclusion criterion was the need to re-prescribe genetically engineered biological therapy (GEBT). The severity of the patient's condition was assessed according to the early warning score (NEWS2), the volume of lung tissue lesions was assessed according to computed tomography (CT). Laboratory monitoring included counting the absolute (abs) number of lymphocytes, serum levels of C-reactive protein (CRP), interleukin 6 (IL-6), D-dimer, lactate dehydrogenase, fibrinogen. Statistical data processing was conducted by nonparametric methods using the IBM SPSS Statistics V-22 software. RESULTS: The phenotype of a patient with a negative outcome prognosis was described: a male patient over 50 years of age with aggravated premorbid background (with cardiovascular diseases, obesity and/or chronic renal disease), lung lesion CT 34, saturation less than 93% upon inhalation of atmospheric air, persisting for 2448 hours after GEBT. According to the blood test, lymphopenia was below 1000 U/L and CRP levels were above 50 mg/L. The laboratory parameters and clinical picture of the patient progressively worsened after 911 days of illness, regardless of the use of Anti-IL-6R. The features of patients monitoring when administering IL-6 receptor blockers have been determined. CONCLUSION: IL-6 receptor blockers should be administered to patients hospitalized with severe COVID-19 before the development of hyperinflammatory reactions. The optimal "therapeutic window" is 78 days of illness.

[Results of decision support system implementation for prescribing anticoagulants to patients with atrial fibrillation in hospital].

BACKGROUND: In 819% of patients with atrial fibrillation (AF) with anticoagulant therapy (ACT), hemorrhagic complications occur, including due to excess doses of AC. At the same time, ACT is necessary for patients with AF, since anticoagulants effectively reduces the risk of ischemic stroke. To make a decision on the appointment of ACT, it is necessary to correlate the risks of ischemic stroke and bleeding, this requires knowledge of current clinical using ACT recommendations and instructions. Among patients admitted to hospital, 30% receive ACT, so increasing adherence to clinical recommendations for prescribing AC to patients with AF by doctors of various profiles is an urgent task. AIM: To analyze the adherence of physicians to recommendations for prescribing ACT before and after the introduction of decision support system (DSS) in patients with AF in a multi-specialty hospital. MATERIALS AND METHODS: A single-center non-randomized study with historical control to assess adherence to recommendations based on the analysis of medical prescriptions and the structure of drug errors in patients with AF in a multi-specialty hospital in Moscow before and after the introduction of DSS. Compliance with the recommendations of physicians was evaluated in the sections indications /contraindications to AC and dosage regimen of AC. The presence of deviations from the clinical recommendations /instructions for medical use of AC was regarded as management of the patient with non-compliance with recommendations. Physicians adherence level to recommendations was calculated as the ratio of cases of compliance with recommendations to the total number of cases. RESULTS: In the control and experimental groups, there was a significant increase in the proportion of POAC at discharge in comparison with admission to hospital: from 54.5 to 76.8% (p=0.0005) and from 63 to 85.7% (p=0.0002), respectively. However, only in the experimental group it was possible to significantly reduce the number of patients without a prescribed ACT (if there are indications) from 7.6 to 1% (p=0.04) in comparison with admission. During the study, it was possible to significantly increase physicians adherence level to the recommendations for the AC dosage regimen in patients with AF from 59% (44 discrepancies for 107 prescriptions) to 84.6% (16 discrepancies for 104 prescriptions); p0.005. Before the introduction of the DSS, the analysis of drug prescriptions revealed 56 drug errors (0.5 errors per patient), after the introduction of the DSS, the number of drug errors significantly decreased to 21 (0.2 errors per patient); p0.05. After the introduction of DSS, the number of sub-therapeutic doses of AC was reduced from 31 (27.7%) to 8 (7.6%); p0.05. CONCLUSION: The level of adherence to the recommendations for prescribing ACT to patients with AF in the hospital is high. The use of DSS increases the level of adherence to the recommendations on the AC dosage regimen in patients with AF, as well as eliminates errors in calculating the risk of ischemic stroke and systemic thromboembolic complications, and contributes to reducing the frequency of prescribing sub-therapeutic doses of AC.

New semi-analytical solution of the problem of vapor bubble growth in superheated liquid.

This paper presents a mathematical model of the vapor bubble growth in an initially uniformly superheated liquid. This model takes into account simultaneously the dynamic and thermal effects and includes the well-known classical equations: the Rayleigh equation and the heat conductivity equation, written with consideration of specifics associated with the process of liquid evaporation. We have obtained a semi-analytical solution to the problem, which consists in reducing the initial boundary value problem with a moving boundary to a system of ordinary differential equations of the first order, valid in a wide range of operating parameters of the process at all its stages: from inertial to thermal, including the transitional one. It is shown that at large times this solution is consistent with the known solutions of other authors obtained in the framework of the energy thermal model, in particular, for the high Jacob numbers, it is consistent with the Plesset-Zwick solution.

[Thrombectomy for acute iliofemoral thrombosis in prevention of pulmonary embolism]. / Trombéktomiia pri ostrom podvzdoshno-bedrennom tromboze v profilaktike TÉLA.

BACKGROUND: Acute thrombosis in the system of the inferior vena cava is one of the most common vascular diseases and is of serious danger as a potential source of one of the most severe complications. In order to assess efficacy of open thrombectomy for embologenic iliofemoral venous thromboses we carried out comparison of the results of open thrombectomy and implantation of cava filters in a total of 119 patients presenting with iliofemoral thrombosis. PATIENTS AND METHODS: Open thrombectomy was performed in a total of 59 patients. Of these, 12 patients with segmental thromboses underwent radical thrombectomy and 47 patients with disseminated forms of thrombosis were subjected to partial thrombectomy with plication of the femoral vein. In 5 patients, the operation was supplemented with applying an arteriovenous fistula. Efficacy of operations was assessed with the help of ultrasonographic duplex angioscanning and regression of clinical manifestations. In the remote period, the degree of manifestations of post-thrombotic disease was assessed by means of the Villalta scale. RESULTS: After radical thrombectomy, patency of the iliofemoral segment was preserved in all patients during the whole follow-up period. In the group of patients with partial thrombectomy, 5 (9.5%) patients developed rethrombosis above the placation site at terms from 8 to 12 months. Four-year patency of the iliofemoral segment in this group of patients amounted to 81.5%. In patients with implanted cava filters, neither femoral vein nor iliac segment were patent completely. During the first year, thrombosis of cava filter developed in 9 cases; after 2 years, occlusion of the cava filter was diagnosed in 7 patients. In clinical assessment of the remote results with the use of the Villalta scale in patients after open thrombectomy the symptoms of post-traumatic disease were absent or weakly pronounced. After implantation of the cava filter all patients demonstrated the clinical course of post-traumatic disease, corresponding to 10-15 points. CONCLUSION: Open thrombectomy for iliofemoral embologenic thromboses performed at specialized departments is a radical method of preventing thromboembolic complications and promotes restoration or improvement of venous blood flow in the extremity.

Effect of wetting on nucleation and growth of D2 in confinement.

We have performed a computational study to determine how the wetting of liquid deuterium to the walls of the material influences nucleation. We present the development of a pair-wise interatomic potential that includes zero-point motion of molecular deuterium. Deuterium is used in this study because of its importance to inertial confinement fusion and the potential to generate a superfluid state if the solidification can be suppressed. Our simulations show that wetting dominates undercooling compared to the pore geometries. We observe a transition from heterogeneous nucleation at the confining wall to homogeneous nucleation at the bulk of the liquid (and intermediate cases) as the interaction with the confining wall changes from perfect wetting to non-wetting. When nucleation is heterogeneous, the temperature needed for solidification changes by 4 K with decreasing deuterium-wall interaction, but it remains independent (and equal to the one from bulk samples) when homogeneous nucleation dominates. We find that growth and quality of the resulting microstructure also depends on the magnitude of liquid deuterium-wall interaction strength.

Extraction of effective solid-liquid interfacial free energies for full 3D solid crystallites from equilibrium MD simulations.

Molecular dynamics simulations of an embedded atom copper system in the isobaric-isenthalpic ensemble are used to study the effective solid-liquid interfacial free energy of quasi-spherical solid crystals within a liquid. This is within the larger context of molecular dynamics simulations of this system undergoing solidification, where single individually prepared crystallites of different sizes grow until they reach a thermodynamically stable final state. The resulting equilibrium shapes possess the full structural details expected for solids with weakly anisotropic surface free energies (in these cases, ∼5% radial flattening and rounded [111] octahedral faces). The simplifying assumption of sphericity and perfect isotropy leads to an effective interfacial free energy as appearing in the Gibbs-Thomson equation, which we determine to be ∼177 erg/cm2, roughly independent of crystal size for radii in the 50-250 Šrange. This quantity may be used in atomistically informed models of solidification kinetics for this system.

New hydrate formation methods in a liquid-gas medium.

Conceptually new methods of hydrate formation are proposed. The first one is based on the shock wave impact on a water-bubble medium. It is shown that the hydrate formation rate in this process is typically very high. A gas hydrate of carbon dioxide was produced. The process was experimentally studied using various initial conditions, as well as different external action magnitudes. The obtained experimental data are in good agreement with the proposed model. Other methods are based on the process of boiling liquefied gas in an enclosed volume of water (explosive boiling of a hydrating agent and the organization of cyclic boiling-condensation process). The key features of the methods are the high hydrate formation rate combined with a comparatively low power consumption leading to a great expected efficiency of the technologies based on them. The set of experiments was carried out. Gas hydrates of refrigerant R134a, carbon dioxide and propane were produced. The investigation of decomposition of a generated gas hydrate sample was made. The criteria of intensification of the hydrate formation process are formulated.

[The effect of heterozygosity for marker loci on recombination fraction in adjacent chromosomal regions in maize]. / Vliianie geterozigotnosti po markernym lokusam na chastoty rekombinatsii v sosednikh uchastkakh khromosom u kukuruzy.

Analysis of maize F2 plants revealed a decrease in the recombination fraction (rf) between the marker loci in case of heterozygosity of adjacent chromosomal regions. The relative decrease in rf was positively associated with the length of the heterozygous region. Heterozygosity had no effect on rf in other chromosomes. These results can be explained by defective pairing of heterozygous chromosomal regions in meiosis.

Diffraction and imaging study of imperfections of crystallized lysozyme with coherent X-rays.

Phase-contrast X-ray diffraction imaging and high-angular-resolution diffraction combined with phase-contrast radiographic imaging were employed to characterize defects and perfection of a uniformly grown tetragonal lysozyme crystal in the symmetric Laue case. The full-width at half-maximum (FWHM) of a 4 4 0 rocking curve measured from the original crystal was approximately 16.7 arcsec and imperfections including line defects, inclusions and other microdefects were observed in the diffraction images of the crystal. The observed line defects carry distinct dislocation features running approximately along the <1 1 0> growth front and have been found to originate mostly in a central growth area and occasionally in outer growth regions. Inclusions of impurities or formations of foreign particles in the central growth region are resolved in the images with high sensitivity to defects. Slow dehydration led to the broadening of a fairly symmetric 4 4 0 rocking curve by a factor of approximately 2.6, which was primarily attributed to the dehydration-induced microscopic effects that are clearly shown in X-ray diffraction images. The details of the observed defects and the significant change in the revealed microstructures with drying provide insight into the nature of imperfections, nucleation and growth, and the properties of protein crystals.

Surface relaxation in protein crystals.

Surface x-ray diffraction measurements were performed on (111) growth faces of crystals of the cellular iron-storage protein, horse spleen ferritin. Crystal truncation rods (CTR) were measured. A fit of the measured profile of the CTR revealed a surface roughness of 48+/-4.5 A and a top layer spacing contraction of 3.9+/-1.5%. In addition to the peak from the CTR, the rocking curves of the crystals displayed unexpected extra peaks. Multiple scattering is demonstrated to account for them. Future applications of the method could allow the exploration of hydration effects on the growth of protein crystals.

Phase sensitive x-ray diffraction imaging of defects in biological macromolecular crystals.

Conventional x-ray diffraction topography is currently used to map defects in the bulk of protein crystals, but the lack of sufficient contrast is frequently a limiting factor. We experimentally demonstrate that this barrier can be circumvented using a method that combines phase sensitive and diffraction imaging principles. Details of defects revealed in tetragonal lysozyme and cubic ferritin crystals are presented and discussed. The approach enabling the detection of the phase changes of diffracted x rays should prove to be useful in the study of defect structures in a broad range of biological macromolecular crystals.

Laboratory multiple-crystal X-ray topography and reciprocal-space mapping of protein crystals: influence of impurities on crystal perfection.

Double-axis multiple-crystal X-ray topography, rocking-curve measurements and triple-axis reciprocal-space mapping have been combined to characterize protein crystals using a laboratory source. Crystals of lysozyme and lysozyme crystals doped with acetylated lysozyme impurities were examined. It was shown that the incorporation of acetylated lysozyme into crystals of lysozyme induces mosaic domains that are responsible for the broadening and/or splitting of rocking curves and diffraction-space maps along the direction normal to the reciprocal-lattice vector, while the overall elastic lattice strain of the impurity-doped crystals does not appear to be appreciable in high angular resolution reciprocal-space maps. Multiple-crystal monochromatic X-ray topography, which is highly sensitive to lattice distortions, was used to reveal the spatial distribution of mosaic domains in crystals which correlates with the diffraction features in reciprocal space. Discussions of the influence of acetylated lysozyme on crystal perfection are given in terms of our observations.

Macromolecular impurities and disorder in protein crystals.

The mechanisms by which macromolecular impurities degrade the diffraction properties of protein crystals have been investigated using X-ray topography, high-resolution diffraction line shape measurements, crystallographic data collection, chemical analysis, and two-photon excitation fluorescence microscopy. Hen egg-white lysozyme crystals grown from solutions containing a structurally unrelated protein (ovotransferrin) and a related protein (turkey egg-white lysozyme) can exhibit significantly broadened mosaicity due to formation of cracks and dislocations but have overall B factors and diffraction resolutions comparable to those of crystals grown from uncontaminated lysozyme. Direct fluorescence imaging of the three-dimensional impurity distribution shows that impurities incorporate with different densities in sectors formed by growth on different crystal faces, and that impurity densities in the crystal core and along boundaries between growth sectors can be much larger than in other parts of the crystal. These nonuniformities create stresses that drive formation of the defects responsible for the mosaic broadening. Our results provide a rationale for the use of seeding to obtain high-quality crystals from heavily contaminated solutions and have implications for the use of crystallization for protein purification. Proteins 1999;36:270-281.