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C40H39SmN8O14, triclinic, P1̄ (no. 2), a = 8.2799(1) Å, b = 16.6666(5) Å, c = 17.1471(3) Å, α = 73.549 (2) ∘ , β = 89.123 (1) ∘ , γ = 83.045(2)°, V = 2252.2(1) Å3, Z = 2, R g t (F) = 0.0592, w R r e f (F2) = 0.1438, T = 297.71(13) K. [ABSTRACT FROM AUTHOR]

In this study, we successfully solve polymorphs A and B of zeolite EMM‐17, which can only crystallize in sub‐micrometer‐sized crystals while containing complex stacking disorders, from the three‐dimensional (3D) electron diffraction (ED) data. This is the first time that the atomic structure of this polymorph has been ab initio solved, and the result reveals a unique 10(12)×10(12)×11‐ring channel system. Moreover, we acquire the first atomic‐resolution images of EMM‐17 using integrated differential phase‐contrast scanning transmission electron microscopy. The images allow us to directly observe polymorphs B and C and discover a large number of local structural defects. Based on structural features unraveled from the reciprocal‐space 3D ED data and real‐space images, we propose a series of energetically feasible local structures in EMM‐17. We also demonstrate that the unique porous structure of EMM‐17 enables efficient kinetic separation of C6 alkane isomers. [ABSTRACT FROM AUTHOR]

Tailoring the morphology of a specific crystalline material through distinct crystal growth mechanisms (classical and nonclassical) is challenging. Herein, we report the two unique morphologies of a medium‐pore (10×8‐ring) zeolite, ZSM‐57, prepared by employing an identical organic structure‐directing agent (OSDA) and different inorganic cations, namely Na+ and K+, denoted as ZSM‐57‐Na (pentagonal nanoplates) and ZSM‐57‐K (pentagonal nanoprisms), respectively. The tunable twin domain size and twin boundaries in both samples have been unraveled at the atomic level by electron crystallography. It is of significance to note that the 10‐ring pore openings run perpendicular to the pentagonal nanoplates and nanoprisms. Moreover, the distinct crystal growth mechanisms, which result in the different unique morphologies and tunable twin domains, were further determined by electron crystallography combined with other techniques. Nonclassical growth involving the aggregation of amorphous aluminosilicate nanoparticles to the smooth ZSM‐57‐Na crystal surface dominates the ZSM‐57‐Na crystallization process. For the ZSM‐57‐K sample, the classical layer‐by‐layer growth through the addition of silica molecules to advancing steps on the crystal surface dominates the ZSM‐57‐K crystallization process. The different morphologies of both samples result in the distinct catalytic lifespan of the methanol conversion and selectivity of lower olefins. Bridging the gap: Tunable nonclassical and classical crystal growth mechanisms in the ZSM‐57 zeolite have been revealed with the aid of electron crystallography (see figure). The different mechanisms lead to zeolites with different unique morphologies and twin domains than can be tuned by varying the metal cation in the reaction medium. The methanol conversion reaction revealed the two zeolites with different morphologies exhibit different catalytic behavior. [ABSTRACT FROM AUTHOR]

The structure solution, prediction, and targeted synthesis of a family of embedded isoreticular zeolites (EIZs) with expanding structural complexity, denoted the RHO family, were reported recently. Here, the naming and building rules of body-centered cubic EIZs with the lta cage as the lattice point are presented. The rearrangement of a pair of pau and d8r cages between two lta cages and its repetitive insertion, combined with the strong reflections and fragment methods, allows the creation of three other new zeolite families, designated the HPO, RHO(b), and KFI families. Among them, the KFI family is found to be the only EIZ family, on the basis of the similarity of structure factor amplitudes and phases of strong reflections, that is, structural coding, within its family members. The structural credibility of this family is confirmed by both local interatomic distances and T−T−T angle analyses. The existence of tetragonal EIZ families is also demonstrated. The overall results provide useful insights into the prediction of unprecedented EIZ families. [ABSTRACT FROM AUTHOR]

C25H34O7, monoclinic, P21 (no. 4), a = 9.24730(10) Å, b = 9.9061(2) Å, c = 12.5907(2) Å, β = 101.264(2)°, V = 1131.15(3) Å3, Z = 2, Rgt(F) = 0.0380, wRref(F2) = 0.1025, T = 173 K. [ABSTRACT FROM AUTHOR]

A novel structural coding approach combining structure solution, prediction, and the targeted synthesis of new zeolites with expanding complexity and embedded isoreticular structures was recently proposed. Using this approach, the structures of two new zeolites in the RHO family, PST-20 and PST-25, were predicted and synthesized. Herein, by extending this approach, the next two higher generation members of this family, PST-26 and PST-28, have been predicted and synthesized. These two zeolites have much larger unit cell volumes (422 655 Å3 and 614 912 Å3, respectively) than those of the lower generations. Their crystallization was confirmed by a combination of both powder X-ray and electron diffraction techniques. Aluminate and water concentrations in the synthetic mixture were found to be the two most critical factors influencing the structural expansion of embedded isoreticular zeolites under the synthetic conditions studied herein. [ABSTRACT FROM AUTHOR]

The prediction and synthesis of new crystal structures enable the targeted preparation of materials with desired properties. Among porous solids, this has been achieved for metal-organic frameworks, but not for the more widely applicable zeolites, where new materials are usually discovered using exploratory synthesis. Although millions of hypothetical zeolite structures have been proposed, not enough is known about their synthesis mechanism to allow any given structure to be prepared. Here we present an approach that combines structure solution with structure prediction, and inspires the targeted synthesis of new super-complex zeolites. We used electron diffraction to identify a family of related structures and to discover the structural 'coding' within them. This allowed us to determine the complex, and previously unknown, structure of zeolite ZSM-25 (ref. 8), which has the largest unit-cell volume of all known zeolites (91,554 cubic ångströms) and demonstrates selective CO2 adsorption. By extending our method, we were able to predict other members of a family of increasingly complex, but structurally related, zeolites and to synthesize two more-complex zeolites in the family, PST-20 and PST-25, with much larger cell volumes (166,988 and 275,178 cubic ångströms, respectively) and similar selective adsorption properties. Members of this family have the same symmetry, but an expanding unit cell, and are related by hitherto unrecognized structural principles; we call these family members embedded isoreticular zeolite structures. [ABSTRACT FROM AUTHOR]

Zeolites are crystalline aluminosilicate framework materials with corner sharing TO4 (T = Al, Si) tetrahedra forming well-defined pores and channels. Many zeolites are built from similar building units (i.e., isolated units, chains or layers), which are connected in different ways to form a variety of topologies. We have identified ten zeolite frameworks that share the same two-dimensional 'butterfly' net containing 5-, 6- and 10-rings: * MRE, FER, MEL, SZR, MFS, MFI, TUN, IMF, BOG and TON. Different orientations of the TO4 tetrahedra within the layer lead to different connectivities between neighboring layers. Some layers are corrugated and some are flat, resulting in different channel systems parallel to the layer. We found some interesting relationships between the unit cell parameters and this channel system that allow the size of the channels and their directions to be deduced from the unit cell dimensions. This may facilitate the prediction of new members of this zeolite family. In addition, other zeolites containing the 'butterfly' layers are also discussed. [ABSTRACT FROM AUTHOR]

The primary role of yeast Ara1, previously mis-annotated as a D-arabinose dehydrogenase, is to catalyze the reduction of a variety of toxic α,β-dicarbonyl compounds using NADPH as a cofactor at physiological pH levels. Here, crystal structures of Ara1 in apo and NADPH-complexed forms are presented at 2.10 and 2.00 Å resolution, respectively. Ara1 exists as a homodimer, each subunit of which adopts an (α/β)8-barrel structure and has a highly conserved cofactor-binding pocket. Structural comparison revealed that induced fit upon NADPH binding yielded an intact active-site pocket that recognizes the substrate. Moreover, the crystal structures combined with computational simulation defined an open substrate-binding site to accommodate various substrates that possess a dicarbonyl group. [ABSTRACT FROM AUTHOR]

Abstract: Quinone oxidoreductase (QOR EC1.6.5.5) catalyzes the reduction of quinone to hydroxyquinone using NADPH as a cofactor. Here we present the crystal structure of the ζ-crystallin-like QOR Zta1 from Saccharomyces cerevisiae in apo-form at 2.00Å and complexed with NADPH at 1.59Å resolution. Zta1 forms a homodimer, with each subunit containing a catalytic and a cofactor-binding domain. Upon NADPH binding to the interdomain cleft, the two domains shift towards each other, producing a better fit for NADPH, and tightening substrate binding. Computational simulation combined with site-directed mutagenesis and enzymatic activity analysis defined a potential quinone-binding site that determines the stringent substrate specificity. Moreover, multiple-sequence alignment and kinetics assays implied that a single-residue change from Arg in lower organisms to Gly in vertebrates possibly resulted in elevation of enzymatic activity of ζ-crystallin-like QORs throughout evolution. [Copyright &y& Elsevier]

Serpins generally serve as inhibitors that utilize a mobile reactive center loop (RCL) as bait to trap protease targets. Here, we present the crystal structure of serpin18 from Bombyx mori at 1.65 Å resolution, which has a very short and stable RCL. Activity analysis showed that the inhibitory target of serpin18 is a cysteine protease rather than a serine protease. Notably, this inhibitiory reaction results from the formation of an intermediate complex, which then follows for the digestion of protease and inhibitor into small fragments. This activity differs from previously reported modes of inhibition for serpins. Our findings have thus provided novel structural insights into the unique inhibitory mechanism of serpin18. Furthermore, one physiological target of serpin18, fibroinase, was identified, which enables us to better define the potential role for serpin18 in regulating fibroinase activity during B. mori development. [ABSTRACT FROM AUTHOR]

Abstract: Glutathione transferases (GSTs) are ubiquitous detoxification enzymes that conjugate hydrophobic xenobiotics with reduced glutathione. The silkworm Bombyx mori encodes four isoforms of GST Omega (GSTO), featured with a catalytic cysteine, except that bmGSTO3-3 has an asparagine substitution of this catalytic residue. Here, we determined the 2.20-Å crystal structure of bmGSTO3-3, which shares a typical GST overall structure. However, the extended C-terminal segment that exists in all the four bmGSTOs occupies the G-site of bmGSTO3-3 and makes it unworkable, as shown by the activity assays. Upon mutation of Asn29 to Cys and truncation of the C-terminal segment, the in vitro GST activity of bmGSTO3-3 could be restored. These findings provided structural insights into the activity regulation of GSTOs. [Copyright &y& Elsevier]

Abstract Aluminophosphate-based (AlPO-based) molecular sieves (MSs), especially silicoaluminophosphates (SAPO), have found increasing commercial use in adsorptive and catalytic applications. Although there are 245 framework type codes (FTCs) deposited in the zeolite database, only 74 of which are considered as AlPO-based MSs. In this article, firstly, the landscape of three-dimensional (3D) AlPO-based MSs in the zeolite database, including SAPOs, AlPOs, and metalloaluminophosphates (MeAPOs), is summarized and categorized. Secondly, inspired by the systematic investigations of two-dimensional (2D) layered silicates from Prof. Wieslaw J. Roth, the structural transformations of 2D SAPO or AlPO layered materials into 3D zeotype frameworks are elucidated. Last but not least, the potential application of the ADOR method is introduced to the SAPO material. This approach has been widely used for synthesizing new zeolites through a series of steps involving an a ssembly, d isassembly, o rganization, r eorganization on the parent germanosilicates. The open question regarding the application of this synthetic method on the unique SAPO ECR-40 is discussed. Graphical abstract Image 1 Highlights • We summarize and categorize aluminophosphate-based (AlPO-based) molecular sieves. • Structural transformations of AlPO-based 2D materials into 3D frameworks are elucidated. • The ADOR method was extended to AlPO-based materials. • AFY -type SAPO molecular sieve starting from ECR-40 may be synthesized through the ADOR approach. [ABSTRACT FROM AUTHOR]

C25H34O7, monoclinic, P21 (no. 4), a = 9.24730(10) Å, b = 9.9061(2) Å, c = 12.5907(2) Å, β = 101.264(2)°, V = 1131.15(3) Å3, Z = 2, Rgt(F) = 0.0380, wRref(F2) = 0.1025, T = 173 K. [ABSTRACT FROM AUTHOR]

Abstract: The yeast Saccharomyces cerevisiae mitochondrial matrix factor Mmf1, a member in the YER057c/Yigf/Uk114 family, participates in isoleucine biosynthesis and mitochondria maintenance. Mmf1 physically interacts with another mitochondrial matrix protein Mam33, which is involved in the sorting of cytochrome b 2 to the intermembrane space as well as mitochondrial ribosomal protein synthesis. To elucidate the structural basis for their interaction, we determined the crystal structures of Mmf1 and Mam33 at 1.74 and 2.10Å, respectively. Both Mmf1 and Mam33 adopt a trimeric structure: each subunit of Mmf1 displays a chorismate mutase fold with a six-stranded β-sheet flanked by two α-helices on one side, whereas a subunit of Mam33 consists of a twisted six-stranded β-sheet surrounded by five α-helices. Biochemical assays combined with structure-based computational simulation enable us to model a putative complex of Mmf1–Mam33, which consists of one Mam33 trimer and two tandem Mmf1 trimers in a head-to-tail manner. The two interfaces between the ring-like trimers are mainly composed of electrostatic interactions mediated by complementary negatively and positively charged patches. These results provided the structural insights into the putative function of Mmf1 during mitochondrial protein synthesis via Mam33, a protein binding to mitochondrial ribosomal proteins. [Copyright &y& Elsevier]