The SAVED domain of the type III CRISPR protease CalpL is a ring nuclease.

Prokaryotic CRISPR-Cas immune systems detect and cleave foreign nucleic acids. In type III CRISPR-Cas systems, the Cas10 subunit of the activated recognition complex synthesizes cyclic oligoadenylates (cOAs), second messengers that activate downstream ancillary effector proteins. Once the viral attack has been weathered, elimination of extant cOA is essential to limit the antiviral response and to allow cellular recovery.

A General Iron-Catalyzed Decarboxylative Oxygenation of Aliphatic Carboxylic Acids.

We report an iron-catalyzed decarboxylative C(sp)-O bond-forming reaction under mild, base-free conditions with visible light irradiation. The transformation uses readily available and structurally diverse carboxylic acids, iron photocatalyst, and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) derivatives as oxygenation reagents. The process exhibits a broad scope in acids possessing a wide range of stereoelectronic properties and functional groups.

Suberin, the hallmark constituent of bark, identified in a 45-million-year-old monkeyhair tree (Coumoxylon hartigii) from Geiseltal, Germany.

Suberin, a complex biopolymer, forms a water- and gas-insoluble barrier that protects the inner tissues of plants. It is abundant in tree bark, particularly in the cork oak Quercus suber. Anatomically, fossil bark has been described since the Devonian.

Molecular Taphonomy of Heme: Chemical Degradation of Hemin under Presumed Fossilization Conditions.

The metalloporphyrin heme acts as the oxygen-complexing prosthetic group of hemoglobin in blood. Heme has been noted to survive for many millions of years in fossils. Here, we investigate its stability and degradation under various conditions expected to occur during fossilization.

Group 6 germylidyne complexes in the gas phase by LIFDI and APCI mass spectrometry.

Although showing fascinating chemical properties and reactivity in solution, heavier tetrelylidyne complexes with M≡E triple bonds have not been studied in the gas phase before due to their high sensitivity towards air and moisture. We selected four group 6 germylidyne complexes, [Cp(PMe)M≡GeAr] (M = Mo (), W (), Ar = 2,6-dimesitylphenyl) and [Tp'(CO)M≡GeAr] (M = Mo (), W (), Tp' = κ--hydridotris(3,5-dimethylpyrazolyl) borate), for a mass-spectrometric study. Liquid Injection Field Desorption Ionization (LIFDI) proved to be a well-suited technique to ionize these sensitive compounds as the spectra show the molecular ions as radical cations and only minor traces of fragmentation or degradation products.

Elucidation of the Bridging Pattern of the Lantibiotic Pseudomycoicidin.

Lantibiotics are post-translationally modified antibiotic peptides with lanthionine thioether bridges that represent potential alternatives to conventional antibiotics. The lantibiotic pseudomycoicidin is produced by Bacillus pseudomycoides DSM 12442 and is effective against many Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus. While prior work demonstrated that pseudomycoicidin possesses one disulfide bridge and four thioether bridges, the ring topology has so far remained unclear.

Chemistry and Analysis of Organic Compounds in Dinosaurs.

This review provides an overview of organic compounds detected in non-avian dinosaur fossils to date. This was enabled by the development of sensitive analytical techniques. Non-destructive methods and procedures restricted to the sample surface, e.

A Family of Heterobimetallic Cubes Shows Spin-Crossover Behaviour Near Room Temperature.

Using 4-(4'-pyridyl)aniline as a simple organic building block in combination with three different aldehyde components together with metal(II) salts gave three different Fe Pt -cubes and their corresponding Zn Pt analogues by employing the subcomponent self-assembly approach. Whereas the use of zinc(II) salts gave rise to diamagnetic cages, iron(II) salts yielded metallosupramolecular cages that show spin-crossover behaviour in solution. The spin-transition temperature T depends on the incorporated aldehyde component, giving a construction kit for the deliberate synthesis of spin-crossover compounds with tailored transition properties.

Distribution, Ecology, Chemistry and Toxicology of Plant Stinging Hairs.

Plant stinging hairs have fascinated humans for time immemorial. True stinging hairs are highly specialized plant structures that are able to inject a physiologically active liquid into the skin and can be differentiated from irritant hairs (causing mechanical damage only). Stinging hairs can be classified into two basic types: -type stinging hairs with the classical "hypodermic syringe" mechanism expelling only liquid, and -type stinging hairs expelling a liquid together with a sharp crystal.

Charge-State-Dependent Fragmentation of [2.2]Based Metallosupramolecular Cyclic Helicates in the Gas Phase.

A detailed mass-spectrometric study provides insight into the gas-phase fragmentation pathways of a cyclic helicate selectively built from four iron(II) centers and six [2.2]cyclophane-based ligands through the subcomponent self-assembly approach. The charge state of the precursor ion, i.

A heterobimetallic tetrahedron from a linear platinum(II)-bis(acetylide) metalloligand.

Employing 4-ethynylaniline as a simple organic ligand we were able to prepare the stable -bis(acetylide)platinum(II) complex [Pt(L)(PBu)] as a linear metalloligand. The reaction of this metalloligand with iron(II) cations and pyridine-2-carbaldehyde according to the subcomponent self-assembly approach yielded decanuclear heterobimetallic tetrahedron [FePt(L)](OTf). Thus, combination of these two design concepts - the subcomponent self-assembly strategy and the complex-as-a-ligand approach - ensured a fast and easy synthesis of large heterobimetallic coordination cages of tetrahedral shape with a diameter of more than 3 nm as a mixture of all three possible -, - and -symmetric diastereomers.

Self-Assembled, Highly Positively Charged, Allyl-Pd Crowns: Cavity-Pocket-Driven Interactions of Fluoroanions.

A series of dodecanuclear highly positively charged homo- and heterometallamacrocycles [{Pd(η -2-Me-C H )} (4-PPh py) {M (tpbz)} ] (M=Pd, Pt; tpbz=1,2,4,5-tetrakis(diphenylphosphanyl)benzene were synthesized by the quantitative self-assembly of {Pd(η -2-Me-C H )} , {M (tpbz)} and 4-PPh py moieties in 2:1:4 molar ratio. The cationic assemblies were obtained as salts of different fluorinated anions with diverse sizes and electronic properties, namely BF , PF , SbF and CF SO . The new crown-like metallamacrocycles showed remarkable differences in their NMR spectra due to the presence of the different counteranions.

Dynamic Complex-to-Complex Transformations of Heterobimetallic Systems Influence the Cage Structure or Spin State of Iron(II) Ions.

Two new heterobimetallic cages, a trigonal-bipyramidal and a cubic one, were assembled from the same mononuclear metalloligand by adopting the molecular library approach, using iron(II) and palladium(II) building blocks. The ligand system was designed to readily assemble through subcomponent self-assembly. It allowed the introduction of steric strain at the iron(II) centres, which stabilizes its paramagnetic high-spin state.

Subcomponent Self-Assembly of a Cyclic Tetranuclear Fe Helicate in a Highly Diastereoselective Self-Sorting Manner.

An enantiomerically pure diamine based on the 4,15-difunctionalized [2.2]paracyclophane scaffold and 2-formylpyridine self-assemble into an optically pure cyclic metallosupramolecular Fe L helicate upon mixing with iron(II) ions in a diastereoselective subcomponent self-assembly process. The cyclic assembly results from steric strain that prevents the formation of a smaller linear dinuclear triple-stranded helicate, and hence, leads to the larger strain-free assembly that fulfils the maximum occupancy rule.

[2.2]Paracyclophane bis(pyridine)-based metallosupramolecular rhombs in the gas phase: Competitive cleavage of non-covalent and weak covalent bonds.

The gas-phase fragmentation behavior of self-assembled metallo-supramolecular rhombs based on an unusual chiral [2.2]paracyclophane bis(pyridine) ligand is studied by collision-induced dissociation mass spectrometry. The fragmentation patterns strongly depend on the charge state of the respective mass-selected aggregate.

Coordination of capsule assembly and cell wall biosynthesis in Staphylococcus aureus.

The Gram-positive cell wall consists of peptidoglycan functionalized with anionic glycopolymers, such as wall teichoic acid and capsular polysaccharide (CP). How the different cell wall polymers are assembled in a coordinated fashion is not fully understood. Here, we reconstitute Staphylococcus aureus CP biosynthesis and elucidate its interplay with the cell wall biosynthetic machinery.

Chiral hydrogen-bonded supramolecular capsules: synthesis, characterization and complexation of C.

Two supramolecular nanocapsules were generated by multi-component self-assembly of the novel bisphosphoric acid (R,R)-6 with suitable bis- and trisamidines. The resulting chiral, hydrogen-bonded capsules are stable even in polar media and at low concentrations and can be employed for the binding of C70-fullerene in solution.

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels-Alder reaction with inverse electron demand.

The mechanism of an L-proline-catalyzed pyridazine formation from acetone and aryl-substituted tetrazines via a Diels-Alder reaction with inverse electron demand has been studied with NMR and with electrospray ionization mass spectrometry. A catalytic cycle with three intermediates has been proposed. An enamine derived from L-proline and acetone acts as an electron-rich dienophile in a [4 + 2] cycloaddition with the electron-poor tetrazine forming a tetraazabicyclo[2.

Probing the gas-phase structure of charge-tagged intermediates of a proline catalyzed aldol reaction - vibrational spectroscopy distinguishes oxazolidinone from enamine species.

An l-proline based catalyst with a charged phenyl-pyridium substituent (1) was used to analyze intermediates of an organocatalyzed aldol reaction by infrared multi-photon dissociation (IRMPD) mass spectrometry after transfer into the gas phase via electrospray ionization (ESI). IRMPD spectra were interpreted with the aid of density functional theory (DFT) computations. A structurally restricted enamine species was used as a reference molecule for the calculated vibrational frequencies.

Bond Dissociation Energies of Metallo-supramolecular Building Blocks: Insight from Fragmentation of Selectively Self-Assembled Heterometallic Metallo-supramolecular Aggregates.

A series of selectively self-assembled metallo-supramolecular square-like macrocycles with unsymmetric ditopic linkers and two different types of metal corners, i.e., {Pd(η-2-Me-CH)} and {M(dppp)} with dppp = 1,3-bis(diphenylphosphino)propane and M = Pd or Pt, have been studied in the gas phase using collision-induced dissociation.

Styrene Polymerization under Ambient Conditions by using a Transient 1,3,2-Diazaphospholane-2-oxyl Complex.

A combined theoretical and experimental study on the formation and reactivity of a P-OTEMP (P-bound TEMPO (TEMPO=2,2,6,6-tetramethyl-piperidin-1-oxyl)) substituted 1,3,2-diazaphospholane W(CO) complex is presented, including DFT-based mechanistic details. The complex possesses a thermally labile O-N bond that cleaves homolytically yielding the transient 1,3,2-diazaphospholane-2-oxyl complex [(CO) W(R PO )], which acts as a radical initiator for styrene polymerization under ambient conditions.

Investigations of the Copper-Catalyzed Oxidative Cross-Coupling of Tetrahydroisoquinolines with Diethylzinc by a Combination of Mass Spectrometric and Electrochemical Methods.

The aerobic oxidative cross-coupling of tetrahydroisoquinolines (THIQs) with diethylzinc catalyzed by CuCl has been examined by means of electrospray mass spectrometry (ESI-MS). Substrates, intermediates, and the product were readily detected. Particular emphasis has been placed on the role of CuCl .

Dinosaur origin of egg color: oviraptors laid blue-green eggs.

Protoporphyrin (PP) and biliverdin (BV) give rise to the enormous diversity in avian egg coloration. Egg color serves several ecological purposes, including post-mating signaling and camouflage. Egg camouflage represents a major character of open-nesting birds which accomplish protection of their unhatched offspring against visually oriented predators by cryptic egg coloration.

An Octanuclear Metallosupramolecular Cage Designed To Exhibit Spin-Crossover Behavior.

By employing the subcomponent self-assembly approach utilizing 5,10,15,20-tetrakis(4-aminophenyl)porphyrin or its zinc(II) complex, 1H-4-imidazolecarbaldehyde, and either zinc(II) or iron(II) salts, we were able to prepare O-symmetric cages having a confined volume of ca. 1300 Å . The use of iron(II) salts yielded coordination cages in the high-spin state at room temperature, manifesting spin-crossover in solution at low temperatures, whereas corresponding zinc(II) salts led to the corresponding diamagnetic analogues.

Synthesis of hydroxyl-functionalized N-heterocyclic carbene gold(i) complexes and peptide conjugates.

The synthesis and characterization of a series of new cationic gold(i) complexes with hydroxyl-functionalized N-heterocyclic carbene (NHC) ligands is described. They are valuable building blocks for further derivatization: as a first example, coupling with amino acids and a dipeptide, respectively, successfully results in amino acid and peptide conjugates that are hard to obtain by other synthetic routes.