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The Effect of gem-Difluorination on the Conformation and Properties of a Model Macrocyclic System

Chem. Sci., 2024, Accepted Manuscript
DOI: 10.1039/D4SC05424E, Edge Article
Open Access
Laurent Knerr, Thomas Cogswell, Marie. Ahlqvist, Richard James Lewis, Anneli Nordqvist, Christian Sköld
Conformational control of drug candidates to engineer improved potency and ADME properties is an ongoing area of research. Macrocyclic rings tend to offer a greater degree of rigidity than non-cyclised...
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Pd/NHC sequentially catalyzed atroposelective synthesis of planar-chiral macrocycles

Chem. Sci., 2024, Advance Article
DOI: 10.1039/D4SC05482B, Edge Article
Open Access
Gongming Yang, Shangde Liu, Shujie Ji, Xingsen Wu, Jian Wang
The unprecedented non-enzymatically atroposelective synthesis of planar-chiral macrocycles via a Pd/NHC sequential catalytic intermolecular macrocyclization is reported.
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From small changes to big gains: pyridinium-based tetralactam macrocycle for enhanced sugar recognition in water

Chem. Sci., 2024, Advance Article
DOI: 10.1039/D4SC06190J, Edge Article
Open Access
Canjia Zhai, Ethan Cross Zulueta, Alexander Mariscal, Chengkai Xu, Yunpeng Cui, Xudong Wang, Huang Wu, Carson Doan, Lukasz Wojtas, Haixin Zhang, Jianfeng Cai, Libin Ye, Kun Wang, Wenqi Liu
Incorporating pyridinium into an anthracene-based macrocycle significantly enhances its sugar binding affinity by increasing hydrogen bonding and expanding the contact surface area.
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Del Aviz, Southern Force, Balmoral, Nyx, Chotipari and Macron excel




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Markets settle lower ahead of key macro data; Sensex falls 230 points

Equity indices Sensex and Nifty close lower due to selling in banking stocks, cautious investors, and global trends




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A macroscopic magneto-optical response resulting from local effects in ferronematic liquid crystals

Soft Matter, 2024, 20,8363-8372
DOI: 10.1039/D4SM00577E, Paper
Xiangshen Meng, Xiaowei Li, Jian Li, Yueqiang Lin, Xiaodong Liu, Zhenghong He
The dynamic rotational behavior of composite chains under a rotating magnetic field was observed. The birefringence and dichroism variations in FNLCs mainly stem from the magnetic response of the composite chains, indicating local effects.
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The role of macrocycles in supramolecular assembly with polymers

Soft Matter, 2024, 20,8549-8560
DOI: 10.1039/D4SM01053A, Review Article
Ruslan Kashapov, Yuliya Razuvayeva, Elena Fedorova, Lucia Zakharova
Supramolecular self-assembly of polymers with macrocycles has attracted the attention because it enables the spontaneous creation of nanostructures with unique properties.
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Macrotech Developers’ net debt rises 43.5% in Q1 on higher capex for land, construction




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Macrotech Developers to initiate housing projects worth ₹10,000 crore by March in MMR, Pune, Bengaluru

New projects come in the wake of Macrotech Developers reporting a 21 per cent increase in sales bookings to a record ₹4,290 crore during the July-September period earlier this month




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Structure determination of difficult-to-crystallize organic molecules by co-crystallization of a phosphorylated macrocycle

Org. Chem. Front., 2024, 11,6358-6366
DOI: 10.1039/D4QO01498G, Research Article
Heng Li, Zhijin Li, Juli Jiang, Chen Lin, Leyong Wang
This work reported that 37 different difficult-to-crystallize guest molecules were co-crystallized with the host macrocycle F[3]A1-[P(O)Ph]3 at room temperature, and the molecular structures of the guests could be determined by SCXRD.
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Folding of a dynamic macrocyclic system to stabilize its cation radical state

Org. Chem. Front., 2024, Advance Article
DOI: 10.1039/D4QO01566E, Research Article
Arnab Dutta, Krzysztof Dzieszkowski, Marco Farinone, Łukasz Orzeł, Krzysztof Kruczała, Monika Kijewska, Miłosz Pawlicki
A precisely designed π-extended system responds to different stimuli by folding the structure, which prevents overoxidation and stabilizes the cation radical.
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Macroporous chitosan/alginate hydrogels crosslinked with genipin accumulate and retain glioblastoma cancer cells

RSC Adv., 2024, 14,35286-35304
DOI: 10.1039/D4RA06197G, Paper
Open Access
  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Lauriane Parès, Sahar Naasri, Lisa Delattre, Hélène Therriault, Benoît Liberelle, Gregory De Crescenzo, Marc-Antoine Lauzon, Nathalie Faucheux, Benoit Paquette, Nick Virgilio
This work demonstrates how macroporous hydrogels can be prepared with porous polylactide molds, and homogeneous solutions of sodium alginate and chitosan crosslinked with genipin, in order to accumulate glioblastoma cancer cells.
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Macrotech Developers to acquire Bain Capital’s stake in three digital infra platform entities for ₹307 crore 

The entities include Bellissimo Digital Infrastructure Development Management Pvt. Ltd., Palava Induslogic 4 Pvt. Ltd., and Bellissimo In City FC Mumbai 1 Pvt. Ltd., facilitated through Securities Purchase Agreements (SPAs).




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High-efficiency non-thermal plasma synthesis of imine macrocycles

React. Chem. Eng., 2024, Advance Article
DOI: 10.1039/D4RE00061G, Paper
Open Access
  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Patrycja Roszkowska, Abbie M. Scholes, James L. Walsh, Timothy L. Easun, Anna G. Slater
Non-thermal plasma synthesis offers efficient access to imine macrocycles.
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Cardamonin protects against diabetic cardiomyopathy by activating macrophage NRF2 signaling through molecular interaction with KEAP1

Food Funct., 2024, 15,11083-11095
DOI: 10.1039/D4FO03543G, Paper
Wenshan Nan, Jialin Yin, Wenhao Hao, Huali Meng, Junduo Wu, Xiao Yin, Hao Wu
Cardamonin inhibited macrophage M1 polarization in diabetic cardiomyopathy by binding to KEAP1, leading to the dissociation of NRF2 from KEAP1. This promoted NRF2 nuclear translocation and antioxidant gene expression in M1 polarized macrophages.
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Macrotech Developers announces 1-for-1 bonus share issue

This is the first time that the company is paying dividend to its shareholders




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Exploring the impact of abnormal coordination in macrocyclic N-heterocyclic carbene ligands on bio-inspired iron epoxidation catalysis

Catal. Sci. Technol., 2024, 14,6259-6269
DOI: 10.1039/D4CY00992D, Paper
Open Access
  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Greta G. Zámbó, Carla A. Esslinger, Michael J. Sauer, Isabelle Rüter, Robert M. Reich, Serhiy Demeshko, Franc Meyer, Fritz E. Kühn
Macrocyclic and abnormal NHC iron complexes are characterised, showing high catalytic activity in epoxidation reaction and potential for ligand design.
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Bis-thiourea and macrocyclic polyamines as binary organocatalysts for the ROP of lactide

Catal. Sci. Technol., 2024, Advance Article
DOI: 10.1039/D4CY00952E, Paper
Open Access
Assunta D'Amato, Maria Voccia, Filippo Bruno, Sara D'Aniello, Lucia Caporaso, Francesco De Riccardis, Irene Izzo, Giorgio Della Sala, Mina Mazzeo
New binary catalysts formed by a bis-thiourea and a series of flexible polyaza-macrocycles are revealed to be efficient catalysts for the ring opening polymerization (ROP) of L-lactide.
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Macroscopic chiral symmetry breaking in gelation of Fmoc-amino acids: homochiral selective secondary nucleation promoted by the choice of solvent or stirring

Nanoscale, 2024, Advance Article
DOI: 10.1039/D4NR04011B, Communication
Kentaro Tashiro
Homochiral selective secondary nucleation, promoted by the choice of solvent or stirring, was suggested as the key process for the emergence of macroscopic chiral symmetry breaking in the gelation of Fmoc amino acids.
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Current progress and frontiers in three-dimensional macroporous carbon-based aerogels for electromagnetic wave absorption: a review

Nanoscale, 2024, Advance Article
DOI: 10.1039/D4NR03738C, Review Article
Han Ding, Bo Hu, Yu Wang, Yunchen Du
This article provides a timely review on the construction of three-dimensional macroporous carbon-based aerogels and their application in the field of electromagnetic absorption.
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Extracellular vesicles produced by 3D cultured MSCs promote wound healing by regulating macrophage activation through ANXA1

Biomater. Sci., 2024, 12,1761-1770
DOI: 10.1039/D3BM02035E, Paper
Hao Deng, Yuheng Jiang, Junhao Deng, Feifan Chang, Junyu Chen, Xinyu Sun, Dongliang Cheng, Zhongqi Wang, Ran Li, Jiang Liu, Yi Li, Licheng Zhang, Pengbin Yin
Extracellular vesicles (EVs) produced by 3D-cultured MSCs can modulate macrophage activation through ANXA1, thereby promoting wound healing.
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Macrophage membrane-camouflaged nanoclusters of ultrasmall iron oxide nanoparticles for precision glioma theranostics

Biomater. Sci., 2024, Advance Article
DOI: 10.1039/D4BM00357H, Paper
Bin Zhang, Rui Yang, Hongwei Yu, Yamin Peng, Haoyu Huang, Meera Moydeen Abdul Hameed, Han Wang, Guixiang Zhang, Mohamed EL-Newehy, Mingwu Shen, Xiangyang Shi, Shaojun Peng
Macrophage membrane-camouflaged nanoclusters of ultrasmall iron oxide nanoparticles can be developed to cross the blood–brain barrier for magnetic resonance imaging and chemo/chemodynamic therapy.
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Retraction: Strontium-doped gelatin scaffolds promote M2 macrophage switch and angiogenesis through modulating the polarization of neutrophils

Biomater. Sci., 2024, 12,2167-2167
DOI: 10.1039/D4BM90023E, Retraction
Open Access
  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Tao Li, Hongtao He, Zezheng Yang, Junjie Wang, Yuxin Zhang, Guangxu He, Jun Huang, Deye Song, Jiangdong Ni, Xiaojun Zhou, Junfeng Zhu, Muliang Ding
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Carisma Therapeutics raises $53 million for CAR-T alternative using macrophages




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NF-{kappa}B mediates lipopolysaccharide-induced alternative pre-mRNA splicing of MyD88 in mouse macrophages [Signal Transduction]

Although a robust inflammatory response is needed to combat infection, this response must ultimately be terminated to prevent chronic inflammation. One mechanism that terminates inflammatory signaling is the production of alternative mRNA splice forms in the Toll-like receptor (TLR) signaling pathway. Whereas most genes in the TLR pathway encode positive mediators of inflammatory signaling, several, including that encoding the MyD88 signaling adaptor, also produce alternative spliced mRNA isoforms that encode dominant-negative inhibitors of the response. Production of these negatively acting alternatively spliced isoforms is induced by stimulation with the TLR4 agonist lipopolysaccharide (LPS); thus, this alternative pre-mRNA splicing represents a negative feedback loop that terminates TLR signaling and prevents chronic inflammation. In the current study, we investigated the mechanisms regulating the LPS-induced alternative pre-mRNA splicing of the MyD88 transcript in murine macrophages. We found that 1) the induction of the alternatively spliced MyD88 form is due to alternative pre-mRNA splicing and not caused by another RNA regulatory mechanism, 2) MyD88 splicing is regulated by both the MyD88- and TRIF-dependent arms of the TLR signaling pathway, 3) MyD88 splicing is regulated by the NF-κB transcription factor, and 4) NF-κB likely regulates MyD88 alternative pre-mRNA splicing per se rather than regulating splicing indirectly by altering MyD88 transcription. We conclude that alternative splicing of MyD88 may provide a sensitive mechanism that ensures robust termination of inflammation for tissue repair and restoration of normal tissue homeostasis once an infection is controlled.






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Malta rattles EU with Irini withdrawal, Macron and Merkel schedule calls

Malta withdrawal from Operation Irini signals support for Turkish-Libyan corridor, unsettling EU leaders




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Q4 earnings, macro data among 7 factors steering mkt this wk

After an extended period of lockdown, economic stimulus is badly needed.




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The OECD's approach to capital flow management measures used with a macro-prudential intent

This report responds to a request from the G20 that the IMF and OECD assess whether further work is needed on their respective approaches to measures which are both macro-prudential and capital flow measures, taking into account their individual mandates. The report was transmitted to G20 Finance Ministers and Central Bank Governors at their meeting on 16-17 April 2015 in Washington D.C.




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Co-operation on approaches to macro-prudential and capital flow management measures: Update by the IMF and the OECD

This update report by the IMF and the OECD was delivered to G20 in February 2016.




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The Macroeconomics of the Circular Economy Transition: A Critical Review of Modelling Approaches - Environment Working Paper

This paper reviews the existing literature on modelling the macroeconomic consequences of the transition to a circular economy. It provides insights into the current state of the art on modelling policies to improve resource efficiency and the transition to a circular economy by examining 24 modelling-based assessments of a circular economy transition.




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Decoupling of wages from productivity: Macro-level facts

This paper provides a quantitative description of decoupling in OECD countries over the past two decades, with the results suggesting that it is explained by declines in both labour shares and the ratio of median to average wages (a partial measure of wage inequality).




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Decoupling of wages from productivity: Macro-level facts

This paper provides a quantitative description of decoupling in OECD countries over the past two decades, with the results suggesting that it is explained by declines in both labour shares and the ratio of median to average wages (a partial measure of wage inequality).




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Macro blogroll for the morning meeting




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X-ray fluorescence detection for serial macromolecular crystallography using a JUNGFRAU pixel detector

Detection of heavy elements, such as metals, in macromolecular crystallography (MX) samples by X-ray fluorescence is a function traditionally covered at synchrotron MX beamlines by silicon drift detectors, which cannot be used at X-ray free-electron lasers because of the very short duration of the X-ray pulses. Here it is shown that the hybrid pixel charge-integrating detector JUNGFRAU can fulfill this function when operating in a low-flux regime. The feasibility of precise position determination of micrometre-sized metal marks is also demonstrated, to be used as fiducials for offline prelocation in serial crystallography experiments, based on the specific fluorescence signal measured with JUNGFRAU, both at the synchrotron and at SwissFEL. Finally, the measurement of elemental absorption edges at a synchrotron beamline using JUNGFRAU is also demonstrated.




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Investigating increasingly complex macromolecular systems with small-angle X-ray scattering

A review of recent and ongoing development and results within the field of biological solution small-angle X-ray scattering (BioSAXS), with a focus on the increasing complexity of biological samples, data collection and data evaluation strategies.




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Macromolecular X-ray crystallography: soon to be a road less travelled?

From the perspective of a young(ish) structural biologist who currently specialises in macromolecular X-ray crystallography, are the best years of crystallography over? Some evidence and hopefully thought-provoking analysis is presented here on the subject.




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Optimization of crystallization of biological macromolecules using dialysis combined with temperature control

A rational way to find the appropriate conditions to grow crystal samples for bio-crystallography is to determine the crystallization phase diagram, which allows precise control of the parameters affecting the crystal growth process. First, the nucleation is induced at supersaturated conditions close to the solubility boundary between the nucleation and metastable regions. Then, crystal growth is further achieved in the metastable zone – which is the optimal location for slow and ordered crystal expansion – by modulation of specific physical parameters. Recently, a prototype of an integrated apparatus for the rational optimization of crystal growth by mapping and manipulating temperature–precipitant–concentration phase diagrams has been constructed. Here, it is demonstrated that a thorough knowledge of the phase diagram is vital in any crystallization experiment. The relevance of the selection of the starting position and the kinetic pathway undertaken in controlling most of the final properties of the synthesized crystals is shown. The rational crystallization optimization strategies developed and presented here allow tailoring of crystal size and diffraction quality, significantly reducing the time, effort and amount of expensive protein material required for structure determination.




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The early history of cryo-cooling for macromolecular crystallography

This paper recounts the first successful cryo-cooling of protein crystals that demonstrated the reduction in X-ray damage to macromolecular crystals. The project was suggested by David C. Phillips in 1965 at the Royal Institution of Great Britain and continued in 1967 at the Weizmann Institute of Science, where the first cryo-cooling experiments were performed on lysozyme crystals, and was completed in 1969 at Purdue University on lactate dehydrogenase crystals. A 1970 publication in Acta Crystallographica described the cryo-procedures, the use of cryo-protectants to prevent ice formation, the importance of fast, isotropic cryo-cooling and the collection of analytical data showing more than a tenfold decrease in radiation damage in cryo-cooled lactate dehydrogenase crystals. This was the first demonstration of any method that reduced radiation damage in protein crystals, which provided crystallographers with suitable means to employ synchrotron X-ray sources for protein-crystal analysis. Today, fifty years later, more than 90% of the crystal structures deposited in the Protein Data Bank have been cryo-cooled.




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Comparing serial X-ray crystallography and microcrystal electron diffraction (MicroED) as methods for routine structure determination from small macromolecular crystals

Innovative new crystallographic methods are facilitating structural studies from ever smaller crystals of biological macromolecules. In particular, serial X-ray crystallography and microcrystal electron diffraction (MicroED) have emerged as useful methods for obtaining structural information from crystals on the nanometre to micrometre scale. Despite the utility of these methods, their implementation can often be difficult, as they present many challenges that are not encountered in traditional macromolecular crystallography experiments. Here, XFEL serial crystallography experiments and MicroED experiments using batch-grown microcrystals of the enzyme cyclophilin A are described. The results provide a roadmap for researchers hoping to design macromolecular microcrystallography experiments, and they highlight the strengths and weaknesses of the two methods. Specifically, we focus on how the different physical conditions imposed by the sample-preparation and delivery methods required for each type of experiment affect the crystal structure of the enzyme.




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Prediction of models for ordered solvent in macromolecular structures by a classifier based upon resolution-independent projections of local feature data

Current software tools for the automated building of models for macro­molecular X-ray crystal structures are capable of assembling high-quality models for ordered macromolecule and small-molecule scattering components with minimal or no user supervision. Many of these tools also incorporate robust functionality for modelling the ordered water molecules that are found in nearly all macromolecular crystal structures. However, no current tools focus on differentiating these ubiquitous water molecules from other frequently occurring multi-atom solvent species, such as sulfate, or the automated building of models for such species. PeakProbe has been developed specifically to address the need for such a tool. PeakProbe predicts likely solvent models for a given point (termed a `peak') in a structure based on analysis (`probing') of its local electron density and chemical environment. PeakProbe maps a total of 19 resolution-dependent features associated with electron density and two associated with the local chemical environment to a two-dimensional score space that is independent of resolution. Peaks are classified based on the relative frequencies with which four different classes of solvent (including water) are observed within a given region of this score space as determined by large-scale sampling of solvent models in the Protein Data Bank. Designed to classify peaks generated from difference density maxima, PeakProbe also incorporates functionality for identifying peaks associated with model errors or clusters of peaks likely to correspond to multi-atom solvent, and for the validation of existing solvent models using solvent-omit electron-density maps. When tasked with classifying peaks into one of four distinct solvent classes, PeakProbe achieves greater than 99% accuracy for both peaks derived directly from the atomic coordinates of existing solvent models and those based on difference density maxima. While the program is still under development, a fully functional version is publicly available. PeakProbe makes extensive use of cctbx libraries, and requires a PHENIX licence and an up-to-date phenix.python environment for execution.




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Macromolecular structure determination using X-rays, neutrons and electrons: recent developments in Phenix

Diffraction (X-ray, neutron and electron) and electron cryo-microscopy are powerful methods to determine three-dimensional macromolecular structures, which are required to understand biological processes and to develop new therapeutics against diseases. The overall structure-solution workflow is similar for these techniques, but nuances exist because the properties of the reduced experimental data are different. Software tools for structure determination should therefore be tailored for each method. Phenix is a comprehensive software package for macromolecular structure determination that handles data from any of these techniques. Tasks performed with Phenix include data-quality assessment, map improvement, model building, the validation/rebuilding/refinement cycle and deposition. Each tool caters to the type of experimental data. The design of Phenix emphasizes the automation of procedures, where possible, to minimize repetitive and time-consuming manual tasks, while default parameters are chosen to encourage best practice. A graphical user interface provides access to many command-line features of Phenix and streamlines the transition between programs, project tracking and re-running of previous tasks.




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Development of SPACE-II for rapid sample exchange at SPring-8 macromolecular crystallography beamlines

Reducing the sample-exchange time is a crucial issue in maximizing the throughput of macromolecular crystallography (MX) beamlines because the diffraction data collection itself is completed within a minute in the era of pixel-array detectors. To this end, an upgraded sample changer, SPACE-II, has been developed on the basis of the previous model, SPACE (SPring-8 Precise Automatic Cryo-sample Exchanger), at the BL41XU beamline at SPring-8. SPACE-II achieves one sample-exchange step within 16 s, of which its action accounts for only 11 s, because of three features: (i) the implementation of twin arms that enable samples to be exchanged in one cycle of mount-arm action, (ii) the implementation of long-stroke mount arms that allow samples to be exchanged without withdrawal of the detector and (iii) the use of a fast-moving translation and rotation stage for the mount arms. By pre-holding the next sample prior to the sample-exchange sequence, the time was further decreased to 11 s in the case of automatic data collection, of which the action of SPACE-II accounted for 8 s. Moreover, the sample capacity was expanded from four to eight Uni-Pucks. The performance of SPACE-II has been demonstrated in over two years of operation at BL41XU; the average number of samples mounted on the diffractometer in one day was increased from 132 to 185, with an error rate of 0.089%, which counted incidents in which users could not continue with an experiment without recovery work by entering the experimental hutch. On the basis of these results, SPACE-II has been installed at three other MX beamlines at SPring-8 as of July 2019. The fast and highly reliable SPACE-II is now one of the most important pieces of infrastructure for the MX beamlines at SPring-8, providing users with the opportunity to fully make use of limited beamtime with brilliant X-rays.




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The TELL automatic sample changer for macromolecular crystallography

In this paper, the design and functionalities of the high-throughput TELL sample exchange system for macromolecular crystallography is presented. TELL was developed at the Paul Scherrer Institute with a focus on speed, storage capacity and reliability to serve the three macromolecular crystallography beamlines of the Swiss Light Source, as well as the SwissMX instrument at SwissFEL.




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ID30A-3 (MASSIF-3) – a beamline for macromolecular crystallography at the ESRF with a small intense beam

ID30A-3 (or MASSIF-3) is a mini-focus (beam size 18 µm × 14 µm) highly intense (2.0 × 1013 photons s−1), fixed-energy (12.81 keV) beamline for macromolecular crystallography (MX) experiments at the European Synchrotron Radiation Facility (ESRF). MASSIF-3 is one of two fixed-energy beamlines sited on the first branch of the canted undulator setup on the ESRF ID30 port and is equipped with a MD2 micro-diffractometer, a Flex HCD sample changer, and an Eiger X 4M fast hybrid photon-counting detector. MASSIF-3 is recommended for collecting diffraction data from single small crystals (≤15 µm in one dimension) or for experiments using serial methods. The end-station has been in full user operation since December 2014, and here its current characteristics and capabilities are described.




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PDB2INS: bridging the gap between small-molecule and macromolecular refinement

The open-source Python program PDB2INS is designed to prepare a .ins file for refinement with SHELXL [Sheldrick (2015). Acta Cryst. C71, 3–8], taking atom coordinates and other information from a Protein Data Bank (PDB)-format file. If PDB2INS is provided with a four-character PDB code, both the PDB file and the accompanying mmCIF-format reflection data file (if available) are accessed via the internet from the PDB public archive [Read et al. (2011). Structure, 19, 1395–1412] or optionally from the PDB_REDO server [Joosten, Long, Murshudov & Perrakis (2014). IUCrJ, 1, 213–220]. The SHELX-format .ins (refinement instructions and atomic coordinates) and .hkl (reflection data) files can then be generated without further user intervention, appropriate restraints etc. being added automatically. PDB2INS was tested on the 23 974 X-ray structures deposited in the PDB between 2008 and 2018 that included reflection data to 1.7 Å or better resolution in a recognizable format. After creating the two input files for SHELXL without user intervention, ten cycles of conjugate-gradient least-squares refinement were performed. For 96% of these structures PDB2INS and SHELXL completed successfully without error messages.




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A comparison of gas stream cooling and plunge cooling of macromolecular crystals

Cryocooling for macromolecular crystallography is usually performed via plunging the crystal into a liquid cryogen or placing the crystal in a cold gas stream. These two approaches are compared here for the case of nitro­gen cooling. The results show that gas stream cooling, which typically cools the crystal more slowly, yields lower mosaicity and, in some cases, a stronger anomalous signal relative to rapid plunge cooling. During plunging, moving the crystal slowly through the cold gas layer above the liquid surface can produce mosaicity similar to gas stream cooling. Annealing plunge cooled crystals by warming and recooling in the gas stream allows the mosaicity and anomalous signal to recover. For tetragonal thermolysin, the observed effects are less pronounced when the cryosolvent has smaller thermal contraction, under which conditions the protein structures from plunge cooled and gas stream cooled crystals are very similar. Finally, this work also demonstrates that the resolution dependence of the reflecting range is correlated with the cooling method, suggesting it may be a useful tool for discerning whether crystals are cooled too rapidly. The results support previous studies suggesting that slower cooling methods are less deleterious to crystal order, as long as ice formation is prevented and dehydration is limited.




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Simulation of small-angle X-ray scattering data of biological macromolecules in solution

This article presents IMSIM, an application to simulate two-dimensional small-angle X-ray scattering patterns and, further, one-dimensional profiles from biological macromolecules in solution. IMSIM implements a statistical approach yielding two-dimensional images in TIFF, CBF or EDF format, which may be readily processed by existing data-analysis pipelines. Intensities and error estimates of one-dimensional patterns obtained from the radial average of the two-dimensional images exhibit the same statistical properties as observed with actual experimental data. With initial input on an absolute scale, [cm−1]/c[mg ml−1], the simulated data frames may also be scaled to absolute scale such that the forward scattering after subtraction of the background is proportional to the molecular weight of the solute. The effects of changes of concentration, exposure time, flux, wavelength, sample–detector distance, detector dimensions, pixel size, and the mask as well as incident beam position can be considered for the simulation. The simulated data may be used in method development, for educational purposes, and also to determine the most suitable beamline setup for a project prior to the application and use of the actual beamtime. IMSIM is available as part of the ATSAS software package (3.0.0) and is freely available for academic use (http://www.embl-hamburg.de/biosaxs/download.html).




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Optimization of crystallization of biological macromolecules using dialysis combined with temperature control

This article describes rational strategies for the optimization of crystal growth using precise in situ control of the temperature and chemical composition of the crystallization solution through dialysis, to generate crystals of the specific sizes required for different downstream structure determination approaches.