Chemoproteomic discovery of a covalent allosteric inhibitor of WRN helicase

WRN helicase is a promising target for treatment of cancers with microsatellite instability (MSI) due to its essential role in resolving deleterious non-canonical DNA structures that accumulate in cells with faulty mismatch repair mechanisms1-5. Currently there are no approved drugs directly targeting human DNA or RNA helicases, in part owing to the challenging nature of developing potent and selective compounds to this class of proteins. Here we describe the chemoproteomics-enabled discovery of a clinical-stage, covalent allosteric inhibitor of WRN, VVD-133214. This compound selectively engages a cysteine (C727) located in a region of the helicase domain subject to interdomain movement during DNA unwinding. VVD-133214 binds WRN protein cooperatively with nucleotide and stabilizes compact conformations lacking the dynamic flexibility necessary for proper helicase function, resulting in widespread double-stranded DNA breaks, nuclear swelling and cell death in MSI-high (MSI-H), but not in microsatellite-stable, cells. The compound was well tolerated in mice and led to robust tumour regression in multiple MSI-H colorectal cancer cell lines and patient-derived xenograft models. Our work shows an allosteric approach for inhibition of WRN function that circumvents competition from an endogenous ATP cofactor in cancer cells, and designates VVD-133214 as a promising drug candidate for patients with MSI-H cancers.

Zirconium arene triple-decker sandwich complexes: synthesis, electronic structure and bonding

Reduction of a permethylpentalene zirconium(iv) chloride complex [η⁸-Pn*Zr(μ-Cl)_3/2]₂(μ-Cl)₂Li·THF_x with KC₈ in benzene results in activation of the aromatic solvent to yield an "inverted sandwich" complex, [η⁸-Pn*Zr]₂(μ-η⁶:η⁶-C₆H₆) (1). The reactions in toluene, cumene, o-xylene and m-xylene also yield analogous solvent activated triple-decker sandwich complexes, which have been structurally characterised by single-crystal X-ray diffraction. Edge energies in the Zr K-edge XANES spectra are not distinguishable between 1 and formally Zr(ii) and Zr(iv) reference compounds, suggesting a broad edge structure. DFT calculations best describe the bonding in 1 as highly covalent with frontier molecular orbitals showing almost equal contributions from benzene and the Zr-permethylpentalene fragments.

Editing plants for virus resistance using CRISPR-Cas

This minireview summarizes recent advancements using the clustered regularly interspaced palindromic repeats-associated nuclease systems (CRISPR-Cas) derived from prokaryotes to breed plants resistant to DNA and RNA viruses. The CRISPR-Cas system represents a powerful tool able to edit and insert novel traits into plants precisely at chosen loci offering enormous advantages to classical breeding. Approaches to engineering plant virus resistance in both transgenic and non-transgenic plants are discussed. Iterations of the CRISPR-Cas system, FnCas9 and C2c2 capable of editing RNA in eukaryotic cells offer a particular advantage for providing resistance to RNA viruses which represent the great majority of known plant viruses. Scientists have obtained conflicting results using gene silencing technology to produce transgenic plants resistant to geminiviruses. CRISPR-Cas systems engineered in plants to target geminiviruses have consistently reduced virus accumulation providing increased resistance to virus infection. CRISPR-Cas may provide novel and reliable approaches to control geminiviruses and other ssDNA viruses such as Banana bunchy top virus (BBTV).

A unified approach to ent-atisane diterpenes and related alkaloids: synthesis of (-)-methyl atisenoate, (-)-isoatisine, and the hetidine skeleton

A unified approach to ent-atisane diterpenes and related atisine and hetidine alkaloids has been developed from ent-kaurane (-)-steviol (1). The conversion of the ent-kaurane skeleton to the ent-atisane skeleton features a Mukaiyama peroxygenation with concomitant cleavage of the C13-C16 bond. Conversion to the atisine skeleton (9) features a C20-selective C-H activation using a Suárez modification of the Hofmann-Löffler-Freytag (HLF) reaction. A cascade sequence involving azomethine ylide isomerization followed by Mannich cyclization forms the C14-C20 bond in the hetidine skeleton (8). Finally, attempts to form the N-C6 bond of the hetisine skeleton (7) with a late-stage HLF reaction are discussed. The synthesis of these skeletons has enabled the completion of (-)-methyl atisenoate (3) and (-)-isoatisine (4).

New strategies for natural products containing chroman spiroketals

Two cycloaddition strategies are described that lead to various chroman spiroketals from assorted exocyclic enol ethers. Unlike conventional thermodynamic ketalization strategies, the stereochemical outcome for this approach is determined by a kinetic cycloaddition reaction. Thus, the stereochemical outcome reflects the olefin geometry of the starting materials along with the orientation of the associated transition state. However, the initial kinetic product can also be equilibrated by acid catalysis and reconstituted into a thermodynamic stereochemical arrangement. Thus, these strategies uniquely enable synthetic access to either the thermodynamic or kinetic conformation of the spiroketal stereocenter itself. Applications of these strategies in the syntheses of berkelic acid, β-rubromycin, and paecilospirone are presented along with the use of a chroman spiroketal for the construction of heliespirones A and C.

Total synthesis and repudiation of the helianane family

Total syntheses of two structures purported as (+)-heliananes were completed in six pots. Spectral comparisons, between the synthetic and natural compounds, revealed a misassignment of the eight-membered ring in the heliananes. The key step in the syntheses of the proposed structures and the confirmation of their actual structures was a diastereoselective inverse-demand Diels-Alder reaction between an optically active enol ether and an ortho-quinone methide species, which was generated in situ at low temperature by the sequential addition of methylmagnesium bromide and di-tert-butyl dicarbonate to a salicylaldehyde.

Incorporation of a rapid pregnancy-associated glycoprotein ELISA into a CIDR-Ovsynch resynchronization program for a 28 day re-insemination interval

The objective was to compare two resynchronization programs; one that used a blood-based ELISA for pregnancy-associated glycoproteins (PAG) for pregnancy diagnosis so that non-pregnant cows were re-inseminated at 28 d after first TAI, and another that used transrectal ultrasonography for pregnancy diagnosis so that non-pregnant cows were re-inseminated at 35 d after first TAI. The PAG_resynch cows (n = 103) began CIDR-Ovsynch resynchronization on Day 18 after first TAI (Day 0). On Day 25, the CIDR was removed and pregnancy diagnosis with a PAG ELISA was performed. If a cow was not pregnant on Day 25, she was treated with PGF(2α), treated with GnRH 2 d later (Day 27), and TAI on Day 28. Control cows (n = 99) were observed for estrus until Day 25, when they began an identical CIDR-Ovsynch program with pregnancy diagnosis by transrectal ultrasonography on Day 32. If a cow was not pregnant on Day 32, then she was treated with PGF(2α), treated with GnRH 2 d later (Day 34), and TAI on Day 35. There was no difference in pregnancy per AI (P/AI) for either group at first or second insemination. For cows without pregnancy loss, the interval between first and second (P < 0.001) or second and third (P < 0.016) TAI was shorter for PAG_resynch cows compared with Control cows. The interval between first and second or second and third TAI was not different if pregnancy loss cows were included in the analysis. Plasma progesterone concentrations were similar at PGF(2α) treatment, and plasma estradiol concentrations increased similarly after PGF(2α) treatment for PAG_resynch and Control cows. In conclusion, the 28 d CIDR-Ovsynch resynchronization protocol was comparable to a 35 d CIDR-Ovsynch resynchronization protocol that also included estrus detection. Shortened resynchronization protocols that do not require estrus detection may improve reproductive efficiency in dairy cattle.

Technical note: A rapid enzyme-linked immunosorbent assay blood test for pregnancy in dairy and beef cattle

The ruminant trophoblast produces pregnancy-associated glycoproteins (PAG) that can be detected in the blood of pregnant animals. The objective was to determine the accuracy of a rapid ELISA PAG-based test for the purpose of pregnancy detection in cattle. Blood was sampled from dairy cattle (539 Holstein cows, 173 Holstein heifers, 73 Guernsey cows, 22 Guernsey heifers, and 12 Jersey heifers) and crossbred beef cattle (145 cows and 46 heifers) that were >or=25 d after insemination (range = 25 to 45 d for dairy and 29 to 56 d for beef). Cattle were examined by ultrasonography for detection of pregnancy within 2 d of blood collection. Whole blood or plasma was incubated in a polystyrene tube coated with a monoclonal PAG antibody for 15 min. The tubes were then washed and subjected to sequential incubations with a biotinylated polyclonal PAG antibody (15 min, followed by wash), a horseradish peroxidase-streptavidin solution (15 min, followed by wash), and a peroxidase substrate. Tubes were visually assessed for color after 15 min (clear solution = PAG negative, not pregnant; blue solution = PAG positive, pregnant). Total assay time was approximately 90 min. The ultrasound examination was used as the standard for pregnancy diagnosis. The sensitivity (99.8 +/- 0.2%), specificity (91.7 +/- 1.4%), and negative predictive value (99.7 +/- 0.3%) for the PAG test used in dairy cattle were similar for different breeds and for cows and heifers. The positive predictive value for the test was greater in dairy heifers than in dairy cows (96.5 +/- 1.4% vs. 90.5 +/- 1.7%, respectively). In beef cattle, the sensitivity (100%), specificity (92.3 +/- 3.0%), positive predictive value (95.0 +/- 2.0%), and negative predictive value (100%) for the PAG test were similar for cows and heifers. The accuracy of the test was not different for dairy and beef cattle. In conclusion, the rapid ELISA pregnancy test based on PAG was highly sensitive and specific for pregnancy detection in dairy and beef cattle.

Certifying foreign-trained technologists: should the CSLT change?

The certification of foreign-trained technologists is a very sensitive issue, and the CSLT must proceed with caution in making changes to the system. The policy cannot afford to be too lenient, lest in this litigation-conscious climate an incident were to occur that could undermine the credibility of the certification process. On the other hand, it must not be protectionist and discriminatory. If the labour market does become undersupplied with medical technologists, employers in non-regulated provinces may choose to replace their ranks with non-CSLT-certified employees. If this were to happen to a significant degree, employers might come to rely less and less on the CSLT's stamp of approval. In either case, the value of the CSLT, and the RT itself, is at risk.

Evaluation of the Effects of Extremely Low Frequency Electromagnetic Fields on Movement in the Marine Diatom Amphora coffeaeformis

Published work has shown that population motility in the marine diatom Amphora coffeaeformis can be influenced by externally applied electromagnetic fields (EMFs). Here we report attempts to repeat these experiments, which have been proposed as a model for assessing the effects of EMFs on biological systems. Susceptibility to EMFs was tested using five strains of diatoms on agar plates at a very broad range of field conditions, but no effect on population motility was demonstrated. Exposure period to the EMFs, cell density, and position in the cell cycle had no effect on EMF susceptibility, and the direction and distance moved by the diatoms were not affected by EMFs. When tested after at least a month of preincubation at 20 {mu}T, diatoms of strains #2038, IIIB, and IIIF did show an EMF-induced increase in population motility over control cells (up to ~20%) at conditions predicted by the "ion cyclotron resonance" model, but this effect was ephemeral. Later, IIIB showed a similar increase that was abolished when (1) non-pre-incubated cells were used, (2) the EMF-producing coils were not energized, and (3) even harmonics were used. On observing the response of diatoms to EMFs in real time, a significant increase (~2-fold) in diatom speed over control cells was evident at "ion cyclotron resonance" conditions, using strain #2038 (pre-incubated at 20 {mu}T). The effect was abolished at an even harmonic. We conclude that EMFs can modulate diatom motility, but that the system is, as yet, not consistently reproducible.

The 825-1110 angstroms EUV spectrum of Venus

On 15 August 1994 we launched the EUVS sounding rocket payload to observe the 825-1110 angstrom region of Venus's far ultraviolet airglow spectrum. The EUVS telescope/spectrograph obtained good data at five times higher spectral resolution than was previously available in the far ultraviolet. We present these data and compare our results to those obtained by the Galileo UVS and Venera 11/12 UV spectrophotometers. We identify several new spectral emission features, including both singly ionized nitrogen and molecular nitrogen in Venus's spectrum. We also see evidence for electron-impact-induced emission from CO. Finally, the EUVS data indicate that the "Ar" emissions detected in Venus's far ultraviolet spectrum by Venera 11/12 spectrophotometers are in fact not due to argon, thus eliminating the discrepancy between in situ and remote sensing measurements.

First-generation holographic, grazing-incidence gratings for use in converging, extreme-ultraviolet light beams

We present two holographic recording solutions that produce gratings suitable for use at grazing incidence in the extreme ultraviolet. The rulings are formed when the interference pattern of two spherical wave fronts is recorded on a planar substrate. Each grating is designed to minimize or eliminate the dominant aberration terms in order to maximize the spectral and spatial resolution of the system. In the first design, the dominant astigmatism term in a power-series expansion of the light path function is eliminated; in the second design, the dominant comatic terms are minimized. Each grating is placed directly in a converging light beam at grazing incidence to provide high system efficiency in the extreme ultraviolet. The aberration control afforded by both recording solutions is excellent, providing detector-limited spatial and spectral resolution over much of the usable bandpass. Furthermore, the aberration control is maintained over a wide range of beam speeds and off-axis angles, thereby outperforming conventional varied line-space gratings for use in the extreme ultraviolet. We discuss the methodology used to develop the recording solutions, model and compare the performance of the gratings, and discuss possible space-based applications for these gratings.

Peptidergic transmission in the brain. VI. Behavioral consequences of central activation

Having described a peptidergic transmitter system in the rat brain, we now begin to evaluate its behavioral function. We stimulated cell bodies in the medial amygdaloid nucleus (AME) with indwelling bilateral electrodes. These cell bodies contain a vasopressin-like peptide and send fibers to the hippocampus where the peptide is released upon stimulation. There the peptide inhibits hippocampal output in the awake rat just as it does in the anesthetized rat and in the rat brain slice. The stimulation reorganizes behavior with the same latency and duration as the hippocampal effect. For about 15-20 minutes after the brief stimulus, rats remain motionless with eyes wide open. This "freezing" state is punctuated by episodes of exploratory behavior. The stimulus appears to have a positive affective quality. Review of the literature in light of the present results indicates a probable role for this peptidergic system in the generation of sexual behavior in male rats.

The Spectrum of Comet Austin from 910 to 1180 Å

A spectrum of comet Austin (1988 c(1)) has been obtained from 910 to 1180 A. Three bright emission lines were detected, including a forbidden oxygen line (1128 A), which are attributable to radiative pumping of neutral oxygen by solar Lyman beta. The relative strengths of the observed features should prove to be a useful diagnostic of the physical conditions and radiation fields in cometary comae. In addition, the absence of strong spectral features from highly volatile species such as He, Ar, or N(2) can be used to place constraints on the thermal environment under which the comet was formed and has been processed.

Clinical aspects of granulomatous orchitis

Granulomatous orchitis can present in a variety of forms varying from acute to chronic. Clinically, testicular neoplasm is usually diagnosed and radical orchiectomy is performed, with the correct diagnosis being made on microscopic examination. In this article 6 cases of granulomatous orchitis are presented, with a variety of clinical presentations varying from acute to the more chronic forms.

Detailed electronic description of triple bonds between transition metal atoms and verification by photoelectron spectroscopy

Using the SCF-Xalpha-SW method the ground state electronic structures of (HO)(3)Mo identical withMo(OH)(3), (H(2)N)(3)Mo identical withMo(NH(2))(3), and (Me(2)N)(3)Mo identical withMo(NMe(2)) have been calculated. The results provide a detailed description of the metal-to-metal triple bonds present; some of the more important molecular orbitals are shown in detail as contour diagrams. The energy levels of all filled valence shell/molecular orbitals and the lower virtual orbitals are presented in diagrams. The pi(e(u)) and sigma(a(1g)) orbitals which have large amounts of metal character can be identified as the orbitals primarily responsible for Mo-Mo bonding. Using the transition state technique to allow for relaxation effects, the photoelectron spectra (up to 12 eV) have been calculated for Mo(2)(OH)(6) and Mo(2)(NH(2))(6) and found to compare very well, after applying a constant downshift to correct for inductive effects, with experimental spectra for Mo(2)[OCH(2)C(CH(3))(3)](6) and Mo(2)[N(CH(3))(2)](6). The experimental photoelectron spectra are reported.