A theoretical study of the possible use of electroosmotic flow to extend the read length of DNA sequencing by end-labeled free solution electrophoresis

End-labeled free solution electrophoresis (ELFSE) provides a means of separating DNA with free-solution CE, eliminating the need for gels and polymer solutions which increase the run time and can be difficult to load into a capillary. In free-solution electrophoresis, DNA is normally free-draining and all fragments reach the detector at the same time, whereas ELFSE uses an uncharged label molecule attached to each DNA fragment in order to render the electrophoretic mobility size-dependent. With ELFSE, however, the larger molecules are not separated enough (limiting the read length in the case of ssDNA sequencing) while the smaller ones are overseparated; the larger ones are too fast while the shorter ones are too slow, which is the opposite of traditional gel-based methods. In this article, we show how an EOF could be used to overcome these problems and extend the DNA sequencing read length of ELFSE. This counterflow would allow the larger, previously unresolved molecules more time to separate and thereby increase the read length. Through our theoretical investigation, we predict that an EOF mobility of approximately the same magnitude as that of unlabeled DNA would provide the best results for the regime where all molecules move in the same direction. Even better resolution would be possible for smaller values of EOF which allow different directions of migration; however, the migration times then would become too large. The flow would need to be well controlled since the gain in read length decreases as the magnitude of the counterflow increases; an EOF mobility double that of unlabeled DNA would no longer increase the read length, although ELFSE would still benefit from a reduction in migration time.     

A concise, convergent total synthesis of monocerin

A concise and convergent eight-step synthesis of the antifungal metabolite monocerin 1 is reported. The key step involves an allylsilane metathesis/aldehyde condensation sequence to establish the core 2,3,5-trisubstituted tetrahydrofuran. End-game approaches based around intramolecular Heck chemistry revealed an interesting example of formal 6-endo cyclisation, the origin of which was probed using model substrates. The synthesis was ultimately completed by a strategy involving stepwise oxidative cleavage of the C3-ethenyl substituent.     

Detrapping particles in gel electrophoresis: a numerical study of different pulsed field sequences

Large particles tend to get trapped in dead-ends more often than small particles when electrophoresed in random cross-linked gels. It is known that pulsed electric fields can be used to free particles from these traps, leading to an increase in velocity and improved size separation. Although numerical and theoretical models have been proposed for the mobility of smaller particles in the so-called Ogston sieving limit, the effect of pulsed fields on trapping has not been previously modeled. We present a numerical study of detrapping and we compare our results with those of To and Boyde (To, K.-Y., Boyde, T. R., Electrophoresis 1993, 14, 597). We use an exact numerical method to examine detrapping in various two-dimensional systems of obstacles. We also propose and investigate new ways to optimize the pulse sequence in order to separate particles of different sizes.     

In‐column preparation of a brush‐type chiral stationary phase using click chemistry and a silica monolith

Brush‐type chiral stationary phases (CSP) have been prepared both from a silica monolith and, separately, from 10 μm porous silica beads via a process of in‐column modification including attachment of the chiral selector via copper‐catalyzed azide–alkyne cycloaddition. Azide functionalities were first introduced on the pore surface of each type of support by reaction with 3‐(azidopropyl)trimethoxysilane, followed by immobilization of a proline‐derived chiral selector containing an alkyne moiety. This functionalization reaction was carried out in dimethylformamide (DMF) in the presence of catalytic amounts of copper (I) iodide. The separation performance of these triazole linked stationary phases was demonstrated in enantioseparations of four model analytes, which afforded separation factors as high as 11.4.     

Elektroanalytische Bestimmungen und Trennungen

Ohne Zusammenfassung     

The Stool Volatile Metabolome of Pre-Term Babies

The fecal metabolome in early life has seldom been studied. We investigated its evolution in pre-term babies during their first weeks of life. Multiple (n = 152) stool samples were studied from 51 babies, all <32 weeks gestation. Volatile organic compounds (VOCs) were analyzed by headspace solid phase microextraction gas chromatography mass spectrometry. Data were interpreted using Automated Mass Spectral Deconvolution System (AMDIS) with the National Institute of Standards and Technology (NIST) reference library. Statistical analysis was based on linear mixed modelling, the number of VOCs increased over time; a rise was mainly observed between day 5 and day 10. The shift at day 5 was associated with products of branched-chain fatty acids. Prior to this, the metabolome was dominated by aldehydes and acetic acid. Caesarean delivery showed a modest association with molecules of fungal origin. This study shows how the metabolome changes in early life in pre-term babies. The shift in the metabolome 5 days after delivery coincides with the establishment of enteral feeding and the transition from meconium to feces. Great diversity of metabolites was associated with being fed greater volumes of milk.     

Construction of approximate entropic forces for finitely extensible nonlinear elastic (FENE) polymers

When the stress applied to a Rouse-like polymer chain is large enough, one must use anharmonic entropic spring forces in order to keep the chain contour length from increasing to unphysical values. Although one can derive “exact” equations relating the spring extension to the entropic force produced by a finitely extensible non-linear elastic (FENE) random-walk polymer, such expressions are usually of little interest because their complexity would entail large evaluation times in numerical studies by computer. Moreover, these expressions can rarely be used directly in analytical studies. In this article, we describe a systematic method to construct analytically simple yet numerically accurate expressions to relate the entropic force to the extension of an entropic spring for a random-walk polymer chain in arbitrary dimension d ≥ 2. These expressions are modified Pade approximants which yield the correct asymptotic behaviours in both the small and large extension limits. It is shown that the well-known Warner empirical approximation is but a limiting case (for infinite dimensions).     

Cd/Pt Precursor Solution for Solar H2 Production and in situ Photochemical Synthesis of Pt Single-atom Decorated CdS Nanoparticles

Despite extensive efforts to develop high-performance H₂ evolution catalysts, this remains a major challenge. Here, we demonstrate the use of Cd/Pt precursor solutions for significant photocatalytic H₂ production (154.7 mmol g⁻¹ h⁻¹), removing the need for a pre-synthesized photocatalyst. In addition, we also report simultaneous in situ synthesis of Pt single-atoms anchored CdS nanoparticles (Pt_SA-CdS_IS) during photoirradiation. The highly dispersed in situ incorporation of extensive Pt single atoms on CdS_IS enables the enhancement of active sites and suppresses charge recombination, which results in exceptionally high solar-to-hydrogen conversion efficiency of ≈1 % and an apparent quantum yield of over 91 % (365 nm) for H₂ production. Our work not only provides a promising strategy for maximising H₂ production efficiency but also provides a green process for H₂ production and the synthesis of highly photoactive Pt_SA-CdS_IS nanoparticles.