bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Generation of Dihydropyrimidine Libraries Utilizing Biginelli Multicomponent Chemistry
Authors: Kappe C. Oliver 
Published: August 2003

AbstractWith the emergence of high‐throughput screening in the pharmaceutical industry over a decade ago, synthetic chemists were faced with the challenge of preparing large collections of molecules to satisfy the demand for new screening compounds. The unique exploratory power of multicomponent reactions such as the Ugi four‐component reaction was soon recognized to be extremely valuable to produce compound libraries in a time‐ and cost effective manner. The present review article summarizes strategies for the construction of libraries through another multicomponent reaction, the Biginelli dihydropyrimidine synthesis. In this three‐component condensation dating back to 1893, CH‐acidic carbonyl compounds, aldehydes and urea‐type building blocks combine to assemble a multifunctionalized dihydropyrimidine scaffold. Due to the interesting pharmacological properties associated with the privileged DHPM structures, the Biginelli reaction and related procedures have received increasing attention in recent years. This review details synthetic advances for the construction of Biginelli libraries via solution phase and solid‐phase strategies that are amenable to a high‐throughput or combinatorial format.
QSAR of Adenosine Receptor Antagonists II:
Authors: Roy Kunal 
Published: August 2003

AbstractConsidering potential of selective adenosine receptor subtype ligands in the development of prospective drug candidates, A1 and A3 receptor binding affinity data of 2‐arylpyrazolo[3,4‐c]quinoline derivatives have been subjected to QSAR analyses to explore the physicochemical requirements for selective binding. The study has been carried out with Wang‐Ford charges of the common atoms of the molecules calculated from their energy minimized conformations using AM1 technique. Apart from the charge parameters, physicochemical variables like partition coefficient and molar refractivity of the whole molecules have been used along with suitable indicator variables. The study shows that substituents on the appended 2‐phenyl ring and 4‐amino or 4‐keto substitution on the pyrazolo[3,4‐c]quinoline nucleus modulate the selectivity pattern. Further, negative charge on the quinoline nitrogen and volume and lipophilicity of the whole molecules are important contributors to the selectivity.
Structure‐Viscosity Relationships for Thai Rice Starches
Authors: Noosuk Piyarat , Hill Sandra E. , Pradipasena Pasawadee , Mitchell John R. 
Published: August 2003

AbstractThe viscosities of five Thai rice starches with different amylose contents were measured by rotational rheometry and using a Rapid Visco Analyser. The viscosity response was interpreted in terms of the swelling volume and the structural properties of the granule determined by calorimetry, infrared spectroscopy and X‐ray diffraction.It was found that the waxy rice starches had a higher swelling volume resulting in a higher viscosity than the other rice classes. Critical concentrations for close packing, identified from the concentration where the flow behaviour departs from Newtonian, were 2.5%, 1.5% and 1.10% for the high amylose, medium amylose and waxy rice starch, respectively. An exception to this was a commercial high amylose starch that had a critical concentration similar to the medium amylose category. This was ex‐plained in terms of a relatively higher loss of short‐range molecular order on gelatini‐sation as shown by FTIR for this starch. Medium amylose Jasmine rice starch, extracted from rice that had been aged for 5 months, showed differences in granule size, crystallinity, pasting profile and enthalpy of gelatinisation when compared with the results for starch extracted from freshly harvested rice. This was provisionally interpreted in terms of granule damage during the extraction process, though more work would be required to confirm this interpretation.
Memory and Learning: Cdk5 tells a tail to remember
Authors: Davenport R. John 
Published: August 2003

Scientists have added to the list of proteins that might regulate learning and memory. New work hints that Cdk5--a protein with numerous other functions in the brain--also helps a class of glutamate receptors known as
N
-methyl-D-aspartate (NMDA) receptors function properly as they facilitate learning. Li and colleagues report that Cdk5, a member of the cyclin-dependent kinase family of proteins (which have achieved fame for coordinating the cell cycle), is located near NMDA receptors at synapses. With fluorescent labels that distinguish Cdk5 and the NMDA receptor, the team visualized these proteins in cultured neurons and found that the patterns overlapped. This result suggests that Cdk5 and the NMDA receptor physically associate with each other. To test this idea, the researchers used antibodies to grab Cdk5 from brain extracts. This procedure captured the receptor in addition to Cdk5, indicating that the two bind to each other. The researchers next applied a chemical inhibitor of Cdk5 to slices of hippocampus, the memory center of the brain. This treatment decreases the flow of electrical current through the receptor and blocks long-term potentiation: the persistent strengthening of neuronal signals that many believe is the initial step in making new memories. Other results hint at a possible mechanism: In vitro, Cdk5 can chemically modify the long tail of an NMDA receptor subunit. Although this work is preliminary, it provides an impetus to figure out whether Cdk5 chemically alters NMDA receptors in vivo and whether the modifications alter receptor function.

--R. John Davenport
(At deadline time, full hyperlink and reference information was not yet available.)

B.-S. Li, H. C. Pant, M.-K. Sun, L. Zhang, S. Takahashi, A. B. Kulkarni, W. Ma, L. Vinade, R. O. Brady, Regulation of NMDA receptors by cyclin-dependent kinase-5.
PNAS Early Edition 2
(issue no. 40) (2001).
[Full Text]
Wild Thing: Less-domesticated mice harbor genetic secrets to long life
Authors: Davenport R. John 
Published: August 2003

A life of leisure might seem attractive, but all that coddling could make one's genes go soft. Domesticated mice--selected for their ability to grow quickly, reproduce robustly, and mind their handlers--make experiments easy. Generations of captivity, however, might select against genes that could help them live longer, according to a new study.
In an effort to find mammalian genes that contribute to longevity, Klebanov and colleagues performed two breeding experiments. In each one, they carried out crosses with four strains of inbred mice to produce a genetically mixed population of grandchildren. One strain in each experiment originated from wild mice, while the others came from animals that had been domesticated prior to breeding. Then the researchers looked for genetic markers that tended to show up in long-lived offspring but not in individuals that died at a younger age. The resulting marker patterns led the team to two regions of the genome, one from each experiment, that were associated with longer living mice. The oldest 18% of animals that carried such tracts of DNA outlived the oldest 18% that did not by approximately 4 months. In both cases the markers that are linked to longevity come from strains derived from wild rather than domesticated mice.
No one can explain this result yet, but in general, animals that are larger and reproduce more tend not to live as long as their smaller and less fertile counterparts. Hence, the domestication process could select against genes that extend life-span. The researchers have yet to home in on the presumed longevity gene or genes that reside in the spans of DNA they identified. But the results hint that domesticated mice might lack the aging-related genes that geneticists are so wild about.

S. Klebanov, C. M. Astle, T. H. Roderick, K. Flurkey, J. R. Archer, J. Chen, D. E. Harrison, Maximum life spans in mice are extended by wild strain alleles.
Exp. Biol. Med.
226
, 854-859 (2001).
[Abstract]
[Full Text]

--Suggested by James M. Harper
Obituary: IdG1-030, Long-Lived Mouse
Authors: Miller Richard A. 
Published: August 2003

IdG1-030, the world's oldest normal lab mouse, died peacefully in his sleep on 15 November 2001, at the age of 1449 days, just 11 days shy of what would have been his fourth birthday.
Born and raised in a small plastic cage in Ann Arbor, Michigan, IdG1-030 was one of a set of quintuplets born to a mated pair whose own parents had romped, poor but free, in the barnyards of Moscow, Idaho. He was among the first volunteers for a National Institutes of Health-funded study to determine whether country mice might retain antiaging genes long ago lost by their effete town-and-gown cousins. IdG1-030 spent his entire life within 15 meters of his birthplace on shelf 4B, apparently content with a social circle consisting initially of three other males but then slowly shrinking, over the years, to a single idiosyncratic point. His devoted caretakers describe IdG1-030 as somewhat shy and certainly not prone to complaint, noting that he dealt with his late-life celebrity as the world's oldest living mouse with the same diffidence that typified his earlier, out-of-the-limelight career as just another research subject. His great age (roughly equivalent, at the end, to that of a 137-year-old human) did not, until the last day or two of his final illness, impair his zest for chewing wood chips or for doing pull-ups near the food hopper at the top of his cage.

Although encouraged by his friends and publicists to go for the international all-genotypes longevity record held by the longest lived Snell dwarf mouse (1451 days; see

Flurkey
et al.

), IdG1-030 seemed to have no interest in comparing his own life history with that of puny dwarves or emaciated, calorically restricted rodents. He was clearly willing to accept an asterisk in the record books as the price for a life of ready access to all-you-can-eat meals and the robust enjoyment of a fully loaded anterior pituitary gland.

Although childless (and, indeed, a lifelong virgin), IdG1-030 is survived by nine half-nieces and -nephews, 19 half-grandnieces and -grandnephews, and 28 great half-grandnieces and -grandnephews, all of them currently working in the research field.
--Richard A. Miller
No Truth to the Fountain of Youth
Authors: Olshansky S. Jay , Hayflick Leonard , Carnes Bruce A. 
Published: August 2003

The essay "
No Truth to the Fountain of Youth
" was published in the
Scientific American
special issue

The Science of Staying Young

in June 2002. In this article, the authors explain why it is important for the public to understand that no purported anti-aging remedy available has been shown to be effective.
Temperature and the expression of seven muscle-specific protein genes during embryogenesis in the Atlantic codGadus morhuaL.
Authors: Hall Thomas E. , Cole Nicholas J. , Johnston Ian A. 
Published: August 2003

SUMMARYSeven cDNA clones coding for different muscle-specific proteins (MSPs) were isolated from the fast muscle tissue of Atlantic cod Gadus morhua L. In situ hybridization using cRNA probes was used to characterize the temporal and spatial patterns of gene expression with respect to somite stage in embryos incubated at 4°C, 7°C and 10°C. MyoDtranscripts were first observed in the presomitic mesoderm prior to somite formation, and in the lateral compartment of the forming somites. MyoD expression was not observed in the adaxial cells that give rise to the slow muscle layer, and expression was undetectable by in situhybridization in the lateral somitic mesoderm after the 35-somite stage,during development of the final ∼15 somites. RT-PCR analysis, however,confirmed the presence of low levels of the transcript during these later stages. A phylogenetic comparison of the deduced aminoacid sequences of the full-length MyoD cDNA clone and those from other teleosts, and inference from the in situ expression pattern suggested homology with a second paralogue (MyoD2) recently isolated from the gilthead seabream Sparus aurata. Following MyoD expression,α-actin was the first structural gene to be switched on at the 16-somite stage, followed by myosin heavy chain, troponin T, troponin I and muscle creatine kinase. The final mRNA in the series to be expressed was troponin C. All genes were switched on prior to myofibril assembly. The troponin C sequence was unusual in that it showed the greatest sequence identity with the rainbow trout Oncorhynchus mykiss cardiac/slow form, but was expressed in the fast myotomal muscle and not in the heart. In addition, the third TnC calcium binding site showed a lower level of sequence conservation than the rest of the sequence. No differences were seen in the timing of appearance or rate of posterior progression (relative to somite stage) of any MSP transcripts between embryos raised at the different temperatures. It was concluded that myofibrillar genes are activated asynchronously in a distinct temporal order prior to myofibrillar assembly and that this process was highly canalized over the temperature range studied.
Hepoxilins and trioxilins in barnacles: an analysis of their potential roles in egg hatching and larval settlement
Authors: Vogan Claire L. , Maskrey Ben H. , Taylor Graham W. , Henry Sheelagh , Pace-Asciak Cecil R. , Clare Anthony S. , Rowley Andrew F. 
Published: August 2003

SUMMARY
The barnacle life cycle has two key stages at which eicosanoids are believed to be involved in cellular communication pathways, namely the hatching of nauplii and the settlement of cypris larvae. Barnacle egg-hatching activity has previously been reported to reside in a variety of eicosanoids,including 8-hydroxyeicosapentaenoic acid and a number of tri-hydroxylated polyunsaturated fatty acid derivatives, the trioxilins. The production of the eicosapentaenoic acid metabolite trioxilin A4(8,11,12-trihydroxy-5,9,14,17-eicosatetraenoic acid) by the barnacles Balanus amphitrite and Elminius modestus was confirmed using a combination of high-performance liquid chromatography and gas chromatography, both linked to mass spectrometry. In addition, both species also generated trioxilin A3(8,11,12-trihydroxy-5,9,14-eicosatrienoic acid; an arachidonic acid-derived product), 8,11,12-trihydroxy-9,14,17-eicosatrienoic acid (a ω3 analogue of trioxilin A3; derived from ω3 arachidonic acid) and 10,13,14-trihydroxy-4,7,11,16,19-docosapentaenoic acid (a docosahexaenoic acid-derived product). In contrast to earlier reports, trioxilin A3had no E. modestus egg-hatching activity at any of the concentrations tested (10–9–10–6 mol l–1). The unstable epoxide precursor hepoxilin A3,however, caused significant levels of hatching at 10–6 mol l–1. Furthermore, the stable hepoxilin B3 analogue PBT-3 stimulated hatching at 10–7 mol l–1. Neither trioxilin A3, hepoxilin A3 or PBT-3 at 0.25–30 μmol l–1 served as settlement cues for B. amphitrite cypris larvae.
Recent Advances in Asymmetric CC and C‐Heteroatom Bond Forming Reactions using Polymer‐Bound Catalysts
Authors: Bräse Stefan , Lauterwasser Frank , Ziegert Robert E. 
Published: August 2003

AbstractThe synthesis of enantiomerically pure compounds is one of the major challenges in organic synthesis. In this review, we present the state of the art in asymmetric catalysis using immobilized chiral ligands and complexes for asymmetric CC and C‐heteroatom bond forming reactions. Chiral catalysts based on dendrimers and soluble polymeric supports are considered. In particular, addition reactions to carbon‐carbon double bonds, asymmetric 1,2‐addition reactions using, e.g., dialkylzinc reagents, metal‐catalyzed substitution reactions and cycloaddition reactions are covered. Specific emphasis is placed on enantioselective epoxidation and aldol reactions. A further aspect is the (hetero) Diels–Alder reaction catalyzed by immobilized ligands.
1‐Butyl‐3‐methylimidazolium Tetrafluoroborate ([Bmim]BF4) Ionic Liquid: A Novel and Recyclable Reaction Medium for the Synthesis of vic‐Diamines
Authors: Yadav J. S. , Reddy B. V. S. , Premalatha K. 
Published: August 2003

AbstractAziridines undergo ring opening smoothly with various arylamines in 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim]BF4) or 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim]PF6) ionic liquids under mild and neutral conditions to afford the corresponding vicinal‐diamines in excellent yields with high regioselectivity. The recovered activated ionic liquids are recycled for four to five runs with no loss of activity.
Suzuki–Miyaura Cross‐Coupling With Quasi‐Heterogeneous Palladium
Authors: Conlon David A. , Pipik Brenda , Ferdinand Simone , LeBlond Carl R. , Sowa John R. , Izzo Bill , Collins Paul , Ho Guo‐Jie , Williams J. Michael , Shi Yao‐Jun , Sun Yongkui 
Published: August 2003

AbstractThe Suzuki–Miyaura cross‐coupling reaction using heterogeneous Pd/C has a homogeneous component. The soluble palladium concentration increases during the reaction reaching a maximum at ca. 90% conversion before falling to <4 ppm.
Thin Layer Chromatography for the Detection of Unexpected Reactions in Organometallic Combinatorial Catalysis
Authors: Lavastre Olivier , Touzani Rachid , Garbacia Stefania 
Published: August 2003

AbstractThin layer chromatography (TLC) represents a fast and inexpensive alternative to NMR spectroscopy or analytical methods based on chromatography for the detection of unexpected products in organometallic combinatorial catalysis. This screening test led to the detection of the catalytic system [Ir(COD)Cl]2/PPh3 for isomerisation of diolefinic substrates instead the expected ring closing metathesis (RCM) reaction.
The Effect of Aromatic Ethers on the Trimerisation of Ethylene using a Chromium Catalyst and Aryloxy Ligands
Authors: Morgan David H. , Schwikkard Sianne L. , Dixon John T. , Nair Jerald J. , Hunter Roger 
Published: August 2003

AbstractA catalyst system consisting of a chromium source, a 2,6‐disubstituted phenol and an aromatic ether solvent, on activation with triethylaluminium, is active and selective for the trimerisation of ethylene to form 1‐hexene. The aromatic ether appears to play a role as both solvent and reagent and is pivotal in ensuring both the good activity of the system as well as selectivity to the desired product, 1‐hexene.
Reactions of some phosphorus compounds with cellulose dissolved in aqueous alkaline solution
Authors: Petreuş Oana , Bubulac T. , Petreuş I. , Cazacu Georgeta 
Published: August 2003

AbstractDissolution of cellulose in aqueous hydroxide offers a procedure for regeneration of cotton or wood celluloses. The aqueous NaOH system for dissolving cellulose seems to have considerable potential for fiber production and also as a medium for preparing cellulose derivatives. Reactions with phosphoric and phosphorous acids, phenyl‐ and phenoxy phosphonic dichlorides, and an amido phosphite oligomer on aqueous dissolved cellulose are described. The resulting products are characterized by analytical and spectral methods (infrared and X‐ray diffraction) to determine phosphorus and nitrogen content, substitution degree, and polymerization degree. Particular attention was given to the effects produced by chemical modification on the crystalline pattern of microcrystalline cellulose. Some remarks are also made about the thermooxidative behavior of phosphorylated cellulose. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 327–333, 2003
Harmonic analysis in grease rheology
Authors: Karis Thomas E. , Kono Raymond‐Noël , Jhon Myung S. 
Published: August 2003

AbstractYield stress, and small‐ and large‐ amplitude oscillatory shear measurements were performed on greases in a cone‐plate fixture. Below the yield point, the grease behavior mimics that of a lightly crosslinked polymer. In large‐amplitude oscillations that exceed the yield stress, harmonic distortion appears in the stress waveform. The elastic component of the stress is continuous across the transition, while the viscous, or out‐of‐phase component, is a transient stress that occurs in the high shear rate portion of each oscillation cycle. Our newly proposed viscous slip model accurately reproduces the measured stress waveform for greases, as well as for other yield stress materials. From measured harmonic amplitudes, this model provides the strain amplitude dependence of the elastic modulus and the equivalent of a dynamic yield stress. These properties of channeling grease complement the conventional measurements of yield stress and worked and unworked penetration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 334–343, 2003
Synthesis and characterization of oligo‐2‐hydroxy‐1‐naphthaldehyde and its Schiff base oligomers
Authors: Kaya İsmet , Şenol Dilek 
Published: August 2003

AbstractIn this study, oligo‐2‐hydroxy‐1‐naphthaldehyde (OHNA) was synthesized from the oxidative polycondensation of 2‐hydroxy‐1‐naphthaldehyde (HNA) with air oxygen, NaOCl, and H2O2 in an aqueous alkaline medium at 50–95°C. We determined the products and the oxidative polycondensation reaction conditions of HNA with oxidants such as air oxygen, NaOCl, and H2O2. In these reactions, H2O2 was more active than air oxygen and NaOCl and their optimum reaction conditions were studied. The products were characterized by 1H‐NMR, FTIR, UV–visible, and elemental analysis. The respective number‐average molecular weight, mass‐average molecular weight, and polydispersity index values of OHNA and its Schiff base oligomers (compounds 1, 2, and 3) were found to be 500 g mol−1, 1880 g mol−1, and 3.75 for OHNA; 670 g mol−1, 2490 g mol−1, and 3.71 for compound 1; 390 g mol−1, 1080 g mol−1, and 2.77 for compound 2; and 320 g mol−1, 670 g mol−1, and 1.85 for compound 3. At the optimum reaction conditions, the yields of the reaction products were found to be 77.0% O2, 78.0% H2O2, and 75.4% NaOCl. About 80% of the HNA was converted into OHNA. In addition, new Schiff based oligomers were synthesized from the condensation reaction of OHNA with p‐aminophenol, triethyleneglycol bis(4‐aminophenyl ether), and aniline and their structures and properties were determined. Thermogravimetric and dynamic thermal analyses showed OHNA and its Schiff base oligomers to be stable against thermooxidative decomposition. The weight losses of OHNA and its Schiff base oligomer compounds 1, 2, and 3 were found to be 5% at 175, 225, 190, and 230°C, respectively; 50% at 900, 590, 650, and 620°C, respectively; and 60, 80, 85, and 82%, respectively, at 1000°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 442–450, 2003
Structural effect of prepared and commercial superplasticizers on performance of cement pastes
Authors: Aiad I. , Hafiz A. A. 
Published: August 2003

AbstractThe sodium salt of melamine‐phenol formaldehyde sulfonate (MPhFS), melamine formaldehyde sulfonate (MFS), and phenol formaldehyde sulfonate (PhFS) were prepared according to a four‐step reaction procedure. The four steps of the reaction are hydroxymethylation, sulfonation, low pH condensation, and high pH rearrangement. Fourier transform IR and differential scanning calorimetry spectra were used to determine the structure of the synthesized resins. The effects of MFS, PhFS, MPhFS, and commercial superplasticizers on the rheological properties of cement pastes were investigated using a rotating coaxial viscometer. It was found that the prepared resins enhanced the rheological properties of cement pastes more than commercial ones. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 482–487, 2003