Corrigendum to “Absolute configurations of griseorhodins A and C” [Tetrahedron Lett. 58 (50) (2017) 4721–4723]

The known antibiotic and cytotoxic compounds griseorhodin A (1) and griseorhodin C (2) were produced in solid culture by Streptomyces puniceus AB10, which was isolated from the leaf-cutter ant Acromyrmex rugosus rugosus. Their absolute configurations were unambiguously established as 6S,6aS,7S,8S and 6R,6aS,7S,8R, respectively, using vibrational circular dichroism (VCD) and density functional theory (DFT) calculations.     

MMM-QSAR recognition of ribonucleases without alignment: comparison with an HMM model and isolation from Schizosaccharomyces pombe, prediction, and experimental assay of a new sequence

The study of type III RNases constitutes an important area in molecular biology. It is known that the pac1+ gene encodes a particular RNase III that shares low amino acid similarity with other genes despite having a double-stranded ribonuclease activity. Bioinformatics methods based on sequence alignment may fail when there is a low amino acidic identity percentage between a query sequence and others with similar functions (remote homologues) or a similar sequence is not recorded in the database. Quantitative structure-activity relationships (QSAR) applied to protein sequences may allow an alignment-independent prediction of protein function. These sequences of QSAR-like methods often use 1D sequence numerical parameters as the input to seek sequence-function relationships. However, previous 2D representation of sequences may uncover useful higher-order information. In the work described here we calculated for the first time the spectral moments of a Markov matrix (MMM) associated with a 2D-HP-map of a protein sequence. We used MMMs values to characterize numerically 81 sequences of type III RNases and 133 proteins of a control group. We subsequently developed one MMM-QSAR and one classic hidden Markov model (HMM) based on the same data. The MMM-QSAR showed a discrimination power of RNAses from other proteins of 97.35% without using alignment, which is a result as good as for the known HMM techniques. We also report for the first time the isolation of a new Pac1 protein (DQ647826) from Schizosaccharomyces pombe strain 428-4-1. The MMM-QSAR model predicts the new RNase III with the same accuracy as other classical alignment methods. Experimental assay of this protein confirms the predicted activity. The present results suggest that MMM-QSAR models may be used for protein function annotation avoiding sequence alignment with the same accuracy of classic HMM models.     

Stereoselective synthesis of (Z)-alpha-halo-alpha,beta-unsaturated esters, and amides from aldehydes and trihaloesters or amides promoted by manganese

Preliminary results of a Mn-promoted sequential process directed toward the stereoselective synthesis of different (Z)-alpha-halo-alpha,beta-unsaturated compounds are described.     

CrCl2-promoted stereospecific and stereoselective alkyl- and silylcyclopropanation of alpha,beta-unsaturated amides

An efficient chromium-promoted alkyl- or silylcyclopropanation of alpha,beta-unsaturated amides is described. These reactions can be carried out on (E)- or (Z)-alpha,beta-enamides in which the C-C double bond is di-, or trisubstituted. This process takes place with total stereospecificity and the new stereogenic center is generated with high or total stereoselectivity. Some synthetic applications of the obtained silylcyclopropyl amides are also reported. Two mechanisms based on the generation of carbenoid or carbene complexes have been proposed to explain this cyclopropanation reaction.     

Simultaneous Flow Injection Analysis of Paracetamol and Ascorbic Acid with Multiple Pulse Amperometric Detection

The present work reports a simple and quick strategy for simultaneous determination of paracetamol (PC) and ascorbic acid (AA) in pharmaceutical formulations using flow injection method with multiple pulse amperometric detection. The method allows the resolution of the mixture without chemical pretreatment of the sample or electrode modification or the use of chemometric techniques for data analysis. The compounds are detected by applying four sequential pulses (waveform) in function of time to a three‐electrode amperometric system that uses a wall‐jet cell with gold as working electrode. AA is direct detected at +0.40 V and PC is indirectly detected at 0.0 V by the reduction (desorption) of the oxidation product (N‐acetyl‐p‐benzoquinoneimine) electrochemically generated at +0.65 V. The fourth potential pulse (?0.05 V) is applied for the complete regeneration (cleaning) of the gold electrode surface. The linear response range was optimized between 5 and 24 mg L^?1 for AA and 50 and 240 mg L^?1 for PC. The difference between the two responses ranges (10‐fold) present correlation with the concentration of these compounds in two different pharmaceutical formulations available in the Brazilian market. The analytical frequency was calculated in 60 injections per hour. The use of the proposed methodology for PC quantification in the presence of higher AA concentrations was also carried out. Using the standard addition method, it was possible to detect PC in trace levels (LD=0.2 mg L^?1) in the presence of 880‐fold more of AA (176 mg L^?1).     

Decomposition of dinuclear manganese complexes for the preparation of nanostructured oxide materials

The crystal structures of several dinuclear complexes of manganese are reported, and the decomposition and analysis of the nanostructured products derived from them are presented. 1,4,7,10-Tetraazacyclododecane (cyclen) forms dinuclear complexes 1-4 containing doubly oxo-bridged or oxo-acetato bridging ligands depending on the manganese salt used for the reaction. Doubly oxo-bridged 1 crystallizes in the orthorhombic space group Pnma, a = 22.3850(14) A, b = 9.1934(5) A, c = 13.2424(10) A, V = 2725.2(3) A(3). 2, containing [Mn(SCN)5](3-) conteranions, crystallizes in monoclinic space group I2/a with a = 18.2699(10) A, b = 11.2384(6) A, c = 18.6432(9) A, alpha = 90.00 degrees, beta = 114.510(6) degrees, gamma = 90.00 degrees, V = 3483.0(3) A(3). Oxo-acetato-bridged 3 crystallizes in orthorhombic space group Pca21, a = 13.9322(11) A, b = 16.2332(13) A, c = 14.6794(8) A, V = 3320.0(4) A(3). Compound 4 consists of a templated quasi-one-dimensional manganese oxalate crystallized in the triclinic space group P1, a = 9.5442(11) A, b = 10.3758(10) A, c = 21.851(2) A, alpha = 83.720(12) degrees, beta = 80.106(13) degrees, gamma = 85.457(13) degrees, V = 2114.9(4) A(3). Compounds 1, 3, and 4 decompose to nanostructured oxide materials, which may be isolated in bulk as lamellar-structured particles or microspheres or deposited on substrates.     

Differential Equations with Infinitely Many Derivatives and the Borel Transform

Differential equations with infinitely many derivatives, sometimes also referred to as “nonlocal” differential equations, appear frequently in branches of modern physics such as string theory, gravitation and cosmology. We properly interpret and solve linear equations in this class with a special focus on a solution method based on the Borel transform. This method is a far-reaching generalization of previous studies of nonlocal equations via Laplace and Fourier transforms, see for instance (Barnaby and Kamran, J High Energy Phys 02:40, 2008; Górka et al., Class Quantum Gravity 29:065017, 2012; Górka et al., Ann Henri Poincaré 14:947–966, 2013). We reconsider “generalized” initial value problems within the present approach and we disprove various conjectures found in modern physics literature. We illustrate various analytic phenomena that can occur with concrete examples, and we also treat efficient implementations of the theory.     

Recombinant drugs-on-a-chip: The usage of capillary electrophoresis and trends in miniaturized systems – A review

We present here a critical review covering conventional analytical tools of recombinant drug analysis and discuss their evolution towards miniaturized systems foreseeing a possible unique recombinant drug-on-a-chip device. Recombinant protein drugs and/or pro-drug analysis require sensitive and reproducible analytical techniques for quality control to ensure safety and efficacy of drugs according to regulatory agencies. The versatility of miniaturized systems combined with their low-cost could become a major trend in recombinant drugs and bioprocess analysis. Miniaturized systems are capable of performing conventional analytical and proteomic tasks, allowing for interfaces with other powerful techniques, such as mass spectrometry. Microdevices can be applied during the different stages of recombinant drug processing, such as gene isolation, DNA amplification, cell culture, protein expression, protein separation, and analysis. In addition, organs-on-chips have appeared as a viable alternative to testing biodrug pharmacokinetics and pharmacodynamics, demonstrating the capabilities of the miniaturized systems. The integration of individual established microfluidic operations and analytical tools in a single device is a challenge to be overcome to achieve a unique recombinant drug-on-a-chip device.