bluuebunny/crossref_metadata_2025 huggingface dataset:
TAT peptide on the surface of liposomes affords their efficient intracellular delivery even at low temperature and in the presence of metabolic inhibitors
Authors: Torchilin Vladimir P. , Rammohan Ram , Weissig Volkmar , Levchenko Tatyana S.
Published: July 2002

To achieve an efficient intracellular drug and DNA delivery, attempts were made to target microparticulate drug carriers into cytoplasm bypassing the endocytotic pathway. TAT peptides derived from the HIV-1 TAT protein facilitate intracellular delivery of proteins and small colloidal particles. We demonstrated that relatively large drug carriers, such as 200-nm liposomes, can also be delivered into cells by TAT peptide attached to the liposome surface. Liposomes were fluorescently labeled with membranotropic rhodamine-phosphatidylethanolamine or by entrapping FITC-dextran. Incubation of fluorescent TAT liposomes with mouse Lewis lung carcinoma cells, human breast tumor BT20 cells, and rat cardiac myocyte H9C2 results in intracellular localization of certain liposomes. Steric hindrances for TAT peptide⋅cell interaction (attachment of TAT directly to the liposome surface without spacer or the presence of a high MW polyethylene glycol on the liposome surface) abolish liposome internalization, evidencing the importance of direct contact of TAT peptide with the cell surface. Low temperature or metabolic inhibitors, sodium azide or iodoacetamide, have little influence on the translocation of TAT liposomes into cells, confirming the energy-independent character of this process. The approach may have important implications for drug delivery directly into cell cytoplasm.
UV irradiation augments lymphoid malignancies in mice with one functional copy of wild-type
p53
Authors: Jiang Weidong , Ananthaswamy Honnavara N. , Muller H. Konrad , Ouhtit Allal , Bolshakov Svetlana , Ullrich Stephen E. , El-Naggar Adel K. , Kripke Margaret L.
Published: July 2002

Epidemiological studies have suggested an association between
exposure to solar UV radiation and the incidence of lymphoid
malignancies, which has increased substantially worldwide during the
last two decades. Findings from animal studies have raised the question
of whether UV radiation might influence the development of lymphoid
malignancies by means of its immunosuppressive effect. In this study,
we examined the effect of UV irradiation on the development of lymphoid
malignancies in mice with no or only one functional copy of
p53
. Mice that lack both copies of
p53
spontaneously develop high frequency of lymphoid malignancies in the
thymus and spleen.
p53
heterozygous mice with only one
copy of the wild-type allele also develop lymphoid malignancies, but
with a much lower frequency and a long latent period. In our study
using mice of the C57BL/6 background, only one of the unirradiated
mice lacking one copy of
p53
(
p53
+/−
) spontaneously developed a lymphoid
tumor (6%), whereas 88% of UV-irradiated
p53
+/−
mice developed lymphoid tumors in
the spleen or liver. None of the control or UV-irradiated
p53
wild-type mice developed lymphoid tumors during the
60-week observation period. Both UV-irradiated and unirradiated mice
lacking both copies of
p53
(
p53
−/−
) rapidly developed thymic
lymphomas and/or lymphoid tumors in spleen or liver. All of the
lymphoid tumors tested were of T cell type. The immune responses of the
mice to contact sensitization were identical and were suppressed to the
same extent by UV irradiation regardless of the genotype. These results
indicate that differences in immune reactivity do not account for the
different effects of UV radiation on lymphoid malignancies and, in
addition, that p53 is not required for generation of T cell-mediated
immunity. Interestingly, whereas
p53
mutations or loss
of heterozygosity did not account for the accelerated development of
lymphoid tumors in UV-irradiated
p53
+/−
mice, deletions in the
p16

INK4a

gene
were quite common. These data provide the experimental evidence that UV
irradiation induces lymphoid neoplasms in genetically susceptible mice
and support the hypothesis that extensive sunlight exposure contributes
to the induction of lymphoma in humans.
A novel Rtg2p activity regulates nitrogen catabolism in yeast
Authors: Pierce Michael M. , Maddelein Marie-Lise , Roberts B. Tibor , Wickner Reed B.
Published: July 2002

The inactivity of Ure2p, caused by either a
ure2
mutation or the presence of the [URE3] prion, increases
DAL5
transcription and thus enables
Saccharomyces cerevisiae
to take up ureidosuccinate (USA+). Rtg2p regulates transcription of glutamate-repressible genes by facilitation of the nuclear entry of the Rtg1 and Rtg3 proteins. We find that
rtg2
Δ cells take up USA even without the presence of [URE3]. Thus, the USA+ phenotype of
rtg2
Δ strains is not the result generation of the [URE3] prion but is a regulatory effect. Because
rtg1
Δ or
rtg3
Δ mutations or the presence of glutamate do not produce the USA+ phenotype, this is a novel function of Rtg2p. The USA+ phenotype of
rtg2
Δ strains depends on
GLN3
, is caused by overexpression of
DAL5
, and is blocked by
mks1
Δ, but not by overexpression of Ure2p. These characteristics suggest that Rtg2p acts in the upstream part of the nitrogen catabolism regulation pathway.
Trends and patterns in research and development expenditures in the United States
Authors: Jaffe Adam B.
Published: July 2002

This paper is a review of recent trends in United States
expenditures on research and development (R&D). Real expenditures by
both the government and the private sector increased rapidly between
the mid-1970s and the mid-1980s, and have since leveled off. This is
true of both overall expenditures and expenditures on basic research,
as well as funding of academic research. Preliminary estimates indicate
that about $170 billion was spent on R&D in the United States in 1995,
with ≈60% of that funding coming from the private sector and about
35% from the federal government. In comparison to other countries, we
have historically spent more on R&D relative to our economy than other
advanced economies, but this advantage appears to be disappearing. If
defense-related R&D is excluded, our expenditures relative to the size
of the economy are considerably smaller than those of other similar
economies.
Ribozyme-mediated high resistance against potato spindle tuber viroid in transgenic potatoes
Authors: Yang Xicai , Yie Yin , Zhu Feng , Liu Yule , Kang Liangyi , Wang Xiaofeng , Tien Po
Published: July 2002

A hammerhead ribozyme [R(-)] targeting the minus strand RNA of potato spindle tuber viroid (PSTVd) and a mutated nonfunctional ribozyme [mR(-)] were designed, cloned, and transcribed. As predicted, both monomer and dimer transcripts of the active R(-) ribozyme gene could cleave the PSTVd minus strand dimer RNA into three fragments of 77, 338, and 359 bases
in vitro
at 25 and 50°C. The tandem dimer genes of R(-) and mR(-) were subcloned separately into the plant expression vector pROK2. Transgenic potato plants (cultivar Desirée) were generated by
Agrobacterium tumefaciens
-mediated transformation. Twenty-three of 34 independent transgenic plant lines expressing the active ribozyme R(-) resulted in having high levels of resistance to PSTVd, being free of PSTVd accumulation after challenge inoculation with PSTVd, but the remaining lines showed weaker levels of resistance to PSTVd with low levels of PSTVd accumulation. In contrast, 59 of 60 independent transgenic lines expressing the mutated ribozyme mR(-) were susceptible to PSTVd inoculation and had levels of PSTVd accumulation similar to that of the control plants transformed with the empty vector. The resistance against PSTVd replication was stably inherited to the vegetative progenies.
Expression, stability, and membrane integration of truncation mutants of bovine rhodopsin
Authors: Heymann Jürgen A. W. , Subramaniam Sriram
Published: July 2002

Premature termination of protein synthesis by nonsense mutations is at the molecular origin of a number of inherited disorders in the family of G protein-coupled seven-helix receptor proteins. To understand how such truncated polypeptides are processed by the cell, we have carried out COS-1 cell expression studies of mutants of bovine rhodopsin truncated at the first 1, 1.5, 2, 3, or 5 transmembrane segments (TMS) of the seven present in wild-type opsin. Our experiments show that successful completion of different stages in the cellular processing of the protein [membrane insertion,
N
-linked glycosylation, stability to proteolytic degradation, and transport from the endoplasmic reticulum (ER) membrane] requires progressively longer lengths of the polypeptide chain. Thus, none of the truncations affected the ability of the polypeptides to be integral membrane proteins. C-terminal truncations that generated polypeptides with fewer than two TMS resulted in misorientation and prevented glycosylation at the N terminus, whereas truncations that generated polypeptides with fewer than five TMS greatly destabilized the protein. However, all of the truncations prevented exit of the polypeptide from the ER. We conclude that during the biogenesis of rhodopsin, proper integration into the ER membrane occurs only after the synthesis of at least two TMS is completed. Synthesis of the next three TMS confers a gradual increase in stability, whereas the presence of more than five TMS is necessary for exit from the ER.
Homodimerization of tumor-reactive monoclonal antibodies markedly increases their ability to induce growth arrest or apoptosis of tumor cells
Authors: Ghetie Maria-Ana , Podar Erika M. , Ilgen Amy , Gordon Brian E. , Uhr Jonathan W. , Vitetta Ellen S.
Published: July 2002

Monoclonal antibodies (mAbs) that exert antitumor activity can do so by virtue of their effector function and/or their ability to signal growth arrest or cell death. In this study, we demonstrate that mAbs which have little or no signaling activity—i.e., anti-CD19, CD20, CD21, CD22 and Her-2—can become potent antitumor agents when they are converted into IgG–IgG homodimers. The homodimers exert antigrowth activity by signaling G0/G1arrest or apoptosis, depending upon which cell surface molecule they bind. This activity is specific and, in the case of the anti-CD19 mAb, did not require an Fc portion. These results offer the possibility that homodimers of other tumor-reactive mAbs which have little antitumor activity as monomers might be potent, antitumor agents.
The diversity and evolutionary relationships of the pregnancy-associated glycoproteins, an aspartic proteinase subfamily consisting of many trophoblast-expressed genes
Authors: Xie Sancai , Green Jonathan , Bixby James B. , Szafranska Bozena , DeMartini James C. , Hecht Steven , Roberts R. Michael
Published: July 2002

The pregnancy-associated glycoproteins (PAGs) are structurally related to the pepsins, thought to be restricted to the hooved (ungulate) mammals and characterized by being expressed specifically in the outer epithelial cell layer (chorion/trophectoderm) of the placenta. At least some PAGs are catalytically inactive as proteinases, although each appears to possess a cleft capable of binding peptides. By cloning expressed genes from ovine and bovine placental cDNA libraries, by Southern genomic blotting, by screening genomic libraries, and by using PCR to amplify portions of PAG genes from genomic DNA, we estimate that cattle, sheep, and most probably all ruminant Artiodactyla possess many, possibly 100 or more, PAG genes, many of which are placentally expressed. The PAGs are highly diverse in sequence, with regions of hypervariability confined largely to surface-exposed loops. Nonsynonymous (replacement) mutations in the regions of the genes coding for these hypervariable loop segments have accumulated at a higher rate than synonymous (silent) mutations. Construction of distance phylograms, based on comparisons of PAG and related aspartic proteinase amino acid sequences, suggests that much diversification of the PAG genes occurred after the divergence of the Artiodactyla and Perissodactyla, but that at least one gene is represented outside the hooved species. The results also suggest that positive selection of duplicated genes has acted to provide considerable functional diversity among the PAGs, whose presence at the interface between the placenta and endometrium and in the maternal circulation indicates involvement in fetal–maternal interactions.
Immune regulatory loops determine productive interactions within human T lymphocyte–dendritic cell clusters
Authors: Stuhler G. , Zobywalski A. , Grünebach F. , Brossart P. , Reichardt V. L. , Barth H. , Stevanovic S. , Brugger W. , Kanz L. , Schlossman S. F.
Published: July 2002

Help for the induction of cytolytic T lymphocytes is mediated by dendritic cells (DC) that are conditioned by CD40 signaling. We identified tumor necrosis factor family member CD27L/CD70, which is expressed by cytolytic T lymphocytes on interaction with DC to control CD154 (CD40L) up-regulation on CD45RA+helper T cells for subsequent DC stimulation. The results show that the initiation of a cytolytic immune response is determined by regulatory circuits, requiring simultaneous activation and differentiation of all cells involved in T lymphocyte–DC cluster formation.
A specific transition state for S-peptide combining with folded S-protein and then refolding
Authors: Goldberg Jonathan M. , Baldwin Robert L.
Published: July 2002

We measured the folding and unfolding kinetics of mutants for a simple protein folding reaction to characterize the structure of the transition state. Fluorescently labeled S-peptide analogues combine with S-protein to form ribonuclease S analogues: initially, S-peptide is disordered whereas S-protein is folded. The fluorescent probe provides a convenient spectroscopic probe for the reaction. The association rate constant,
k
on
, and the dissociation rate constant,
k
off
, were both determined for two sets of mutants. The dissociation rate constant is measured by adding an excess of unlabeled S-peptide analogue to a labeled complex (RNaseS*). This strategy allows
k
on
and
k
off
to be measured under identical conditions so that microscopic reversibility applies and the transition state is the same for unfolding and refolding. The first set of mutants tests the role of the α-helix in the transition state. Solvent-exposed residues Ala-6 and Gln-11 in the α-helix of native RNaseS were replaced by the helix destabilizing residues glycine or proline. A plot of log
k
on
vs. log
K
d
for this series of mutants is linear over a very wide range, with a slope of −0.3, indicating that almost all of the molecules fold via a transition state involving the helix. A second set of mutants tests the role of side chains in the transition state. Three side chains were investigated: Phe-8, His-12, and Met-13, which are known to be important for binding S-peptide to S-protein and which also contribute strongly to the stability of RNaseS*. Only the side chain of Phe-8 contributes significantly, however, to the stability of the transition state. The results provide a remarkably clear description of a folding transition state.
The cellular ecology of progressive neoplastic transformation: A clonal analysis
Authors: Chow Ming , Rubin Harry
Published: July 2002

A comparison was made of the competence for neoplastic transformation in three different sublines of NIH 3T3 cells and multiple clonal derivatives of each. Over 90% of the neoplastic foci produced by an uncloned transformed (t-SA′) subline on a confluent background of nontransformed cells were of the dense, multilayered type, but about half of the t-SA′ clones produced only light foci in assays without background. This asymmetry apparently arose from the failure of the light focus formers to register on a background of nontransformed cells. Comparison was made of the capacity for confluence-mediated transformation between uncloned parental cultures and their clonal derivatives by using two nontransformed sublines, one of which was highly sensitive and the other relatively refractory to confluence-mediated transformation. Transformation was more frequent in the clones than in the uncloned parental cultures for both sublines. This was dramatically so in the refractory subline, where the uncloned culture showed no overt sign of transformation in serially repeated assays but increasing numbers of its clones exhibited progressive transformation. The reason for the greater susceptibility of the pure clones is apparently the suppression of transformation among the diverse membership that makes up the uncloned parental culture. Progressive selection toward increasing degrees of transformation in confluent cultures plays a major role in the development of dense focus formers, but direct induction by the constraint of confluence may contribute by heritably damaging cells. In view of our finding of increased susceptibility to transformation in clonal versus uncloned populations, expansion of some clones at the expense of others during the aging process would contribute to the marked increase of cancer with age.
On the behavior of hyperbolic neutral points in two-dimensional ideal magnetohydrodynamics
Authors: Cordoba Diego , Marliani Christiane
Published: July 2002

We study ideal incompressible magnetohydrodynamics in two dimensions. We obtain an exponential estimate on the closing of the angle at hyperbolic saddle points of the magnetic stream function under the assumption that the velocity remains bounded. The analytic results are supported by numerical simulations. These results give evidence against a standard scenario for singularity formation for these equations.
NAPO as a novel marker for apoptosis
Authors: Sayan Berna S. , Ince Gulayse , Sayan A. Emre , Ozturk Mehmet
Published: July 2002

Apoptosis or programmed cell death plays a pivotal role in embryonic development and maintenance of homeostasis. It is also involved in the etiology of pathophysiological conditions such as cancer, neurodegenerative, autoimmune, infectious, and heart diseases. Consequently, the study of apoptosis is now at center of both basic and clinical research applications. Therefore, sensitive and simple apoptosis detection techniques are required. Here we describe a monoclonal antibody–defined novel antigen, namely NAPO (negative in apoptosis), which is specifically lost during apoptosis. The anti-NAPO antibody recognizes two nuclear polypeptides of 60 and 70 kD. The antigen is maintained in quiescent and senescent cells, as well as in different phases of the cell cycle, including mitosis. Thus, immunodetection of NAPO antigen provides a specific, sensitive, and easy method for differential identification of apoptotic and nonapoptotic cells.
Subsecond Induction of α4 Integrin Clustering by Immobilized Chemokines Stimulates Leukocyte Tethering and Rolling on Endothelial Vascular Cell Adhesion Molecule 1 under Flow Conditions
Authors: Grabovsky Valentin , Feigelson Sara , Chen Chun , Bleijs Diederik A. , Peled Amnon , Cinamon Guy , Baleux Francoise , Arenzana-Seisdedos Frenando , Lapidot Tsvee , van Kooyk Yvette , Lobb Roy R. , Alon Ronen
Published: July 2002

Leukocyte recruitment to target tissue is initiated by weak rolling attachments to vessel wall ligands followed by firm integrin-dependent arrest triggered by endothelial chemokines. We show here that immobilized chemokines can augment not only arrest but also earlier integrin-mediated capture (tethering) of lymphocytes on inflamed endothelium. Furthermore, when presented in juxtaposition to vascular cell adhesion molecule 1 (VCAM-1), the endothelial ligand for the integrin very late antigen 4 (VLA-4, α4β1), chemokines rapidly augment reversible lymphocyte tethering and rolling adhesions on VCAM-1. Chemokines potentiate VLA-4 tethering within <0.1 s of contact through Gi protein signaling, the fastest inside-out integrin signaling events reported to date. Although VLA-4 affinity is not altered upon chemokine signaling, subsecond VLA-4 clustering at the leukocyte-substrate contact zone results in enhanced leukocyte avidity to VCAM-1. Endothelial chemokines thus regulate all steps in adhesive cascades that control leukocyte recruitment at specific vascular beds.
Phe-Met-Arg-Phe-amide Activates a Novel Voltage-dependent K+ Current through a Lipoxygenase Pathway in Molluscan Neurones
Authors: Kits K.S. , Lodder J.C. , Veerman M.J.
Published: July 2002

The neuropeptide Phe-Met-Arg-Phe-amide (FMRFa) dose dependently (ED50 = 23 nM) activated a K+ current in the peptidergic caudodorsal neurones that regulate egg laying in the mollusc Lymnaea stagnalis. Under standard conditions ([K+]o = 1.7 mM), only outward current responses occurred. In high K+ salines ([K+]o = 20 or 57 mM), current reversal occurred close to the theoretical reversal potential for K+. In both salines, no responses were measured below −120 mV. Between −120 mV and the K+ reversal potential, currents were inward with maximal amplitudes at ∼−60 mV. Thus, U-shaped current–voltage relations were obtained, implying that the response is voltage dependent. The conductance depended both on membrane potential and extracellular K+ concentration. The voltage sensitivity was characterized by an e-fold change in conductance per ∼14 mV at all [K+]o. Since this result was also obtained in nearly symmetrical K+ conditions, it is concluded that channel gating is voltage dependent. In addition, outward rectification occurs in asymmetric K+ concentrations. Onset kinetics of the response were slow (rise time ∼650 ms at −40 mV). However, when FMRFa was applied while holding the cell at −120 mV, to prevent activation of the current but allow activation of the signal transduction pathway, a subsequent step to −40 mV revealed a much more rapid current onset. Thus, onset kinetics are largely determined by steps preceding channel activation. With FMRFa applied at −120 mV, the time constant of activation during the subsequent test pulse decreased from ∼36 ms at −60 mV to ∼13 ms at −30 mV, confirming that channel opening is voltage dependent. The current inactivated voltage dependently. The rate and degree of inactivation progressively increased from −120 to −50 mV. The current is blocked by internal tetraethylammonium and by bath- applied 4-aminopyridine, tetraethylammonium, Ba2+, and, partially, Cd2+ and Cs+. The response to FMRFa was affected by intracellular GTPγS. The response was inhibited by blockers of phospholipase A2 and lipoxygenases, but not by a cyclo-oxygenase blocker. Bath-applied arachidonic acid induced a slow outward current and occluded the response to FMRFa. These results suggest that the FMRFa receptor couples via a G-protein to the lipoxygenase pathway of arachidonic acid metabolism. The biophysical and pharmacological properties of this transmitter operated, but voltage-dependent K+ current distinguish it from other receptor-driven K+ currents such as the S-current- and G-protein-dependent inward rectifiers.
The Mod-2 cohomology of the Bianchi groups
Authors: Berkove Ethan
Published: July 2002

The Bianchi groups are a family of discrete subgroups of

P
S

L
2

(

C

)

PSL_2(\mathbb C)

which have group theoretic descriptions as amalgamated products and HNN extensions. Using Bass-Serre theory, we show how the cohomology of these two constructions relates to the cohomology of their pieces. We then apply these results to calculate the mod-2 cohomology ring for various Bianchi groups.
PGAAS: a prokaryotic genome assembly assistant system
Authors: Yu Zhou , Li Tao , Zhao Jindong , Luo Jingchu
Published: July 2002

Motivation: In order to accelerate the finishing phase of genome assembly, especially for the whole genome shotgun approach of prokaryotic species, we have developed a software package designated prokaryotic genome assembly assistant system (PGAAS). The approach upon which PGAAS is based is to confirm the order of contigs and fill gaps between contigs through peptide links obtained by searching each contig end with BLASTX against protein databases.

Results: We used the contig dataset of the cyanobacterium Synechococcus sp. strain PCC7002 (PCC7002), which was sequenced with six-fold coverage and assembled using the Phrap package. The subject database is the protein database of the cyanobacterium, Synechocystis sp. strain PCC6803 (PCC6803). We found more than 100 non-redundant peptide segments which can link at least 2 contigs. We tested one pair of linked contigs by sequencing and obtained satisfactory result. PGAAS provides a graphic user interface to show the bridge peptides and pier contigs. We integrated Primer3 into our package to design PCR primers at the adjacent ends of the pier contigs.

Availability: We tested PGAAS on a Linux (Redhat 6.2) PC machine. It is developed with free software (MySQL, PHP and Apache). The whole package is distributed freely and can be downloaded as UNIX compress file: ftp://ftp.cbi.pku.edu.cn/pub/software/unix/pgaas1.0.tar.gz. The package is being continually updated.

Contact: luojc@pku.edu.cn

* To whom correspondence should be addressed.
Exploring the conformational equilibrium of E. coli thioredoxin reductase: Characterization of two catalytically important states by ultrafast flavin fluorescence spectroscopy
Authors: Van Den Berg Petra A.W. , Mulrooney Scott B. , Gobets Bas , Van Stokkum Ivo H.M. , Van Hoek Arie , Williams Charles H. , Visser Antonie J.W.G.
Published: July 2002

The conformational dynamics of wild‐type Escherichia coli thioredoxin reductase (TrxR) and the mutant enzyme C138S were studied by ultrafast time‐resolved fluorescence of the flavin cofactor in combination with circular dichroism (both in the flavin fingerprint and far‐UV regions) and steady‐state fluorescence and absorption spectroscopy. The spectroscopic data show two conformational states of the enzyme (named FO and FR), of which the physical characteristics differ considerably. Ultrafast fluorescence lifetime measurements make it possible to distinguish between the two different populations: Dominant picosecond lifetimes of ∼1 ps (contribution 75%) and 7 ps (8%) are associated with the FO species in TrxR C138S. Long‐lived fluorescence with two time constants in the range of 0.2–1 ns (total contribution 17%) originates from enzyme molecules in the FR conformation. The near absence of fast lifetime components in oxidized wild‐type TrxR supports the idea of this enzyme being predominantly in the FR conformation. The emission spectrum of the FO conformation is blue‐shifted with respect to that of the FR conformation. Because of the large difference in fluorescence characteristics, fluorescence measurements on time scales longer than 100 ps are fully determined by the fraction of enzyme molecules in the FR conformation. Binding of the thiol reagent phenyl mercuric acetate to wild‐type enzyme and TrxR C138S stabilizes the enzymes in the FR conformation. Specific binding of the NADPH‐analog, AADP+, to the FR conformation resulted in dynamic fluorescence quenching in support of the multiple quenching sites model. Raising the temperature from 277K–323K resulted in a moderate shift to the FR conformation for TrxR C138S. High concentrations of the cosolvent glycerol triggered the domain rotation from the FO to the FR conformation.
Alternative type I and I′ turn conformations in the β8/β9 β‐hairpin of human acidic fibroblast growth factor
Authors: Kim Jaewon , Blaber Sachiko I. , Blaber Michael
Published: July 2002

Human acidic fibroblast growth factor (FGF‐1) has a β‐trefoil structure, one of the fundamental protein superfolds. The X‐ray crystal structures of wild‐type and various mutant forms of FGF‐1 have been solved in five different space groups: C2, C2221, P21 (four molecules/asu), P21 (three molecules/asu), and P212121. These structures reveal two characteristically different conformations for the β8/β9 β‐hairpin comprising residue positions 90–94. This region in the wild‐type FGF‐1 structure (P21, four molecules/asu), a his‐tagged His93→Gly mutant (P21, three molecules/asu) and a his‐tagged Asn106→Gly mutant (P212121) adopts a 3:5 β‐hairpin known as a type I (1–4) G1 β‐bulge (containing a type I turn). However, a his‐tagged form of wild‐type FGF‐1 (C2221) and a his‐tagged Leu44→Phe mutant (C2) adopt a 3:3 β‐hairpin (containing a type I′ turn) for this same region. A feature that distinguishes these two types of β‐hairpin structures is the number and location of side chain positions with eclipsed Cβ and main‐chain carbonyl oxygen groups (Ψ ≅ +60°). The effects of glycine mutations upon stability, at positions within the hairpin, have been used to identify the most likely structure in solution. Type I′ turns in the structural data bank are quite rare, and a survey of these turns reveals that a large percentage exhibit crystal contacts within 3.0 Å. This suggests that many of the type I′ turns in X‐ray structures may be adopted due to crystal packing effects.
Acoustic waves generated by pulsed microwaves in viscoelastic rods: Modeling and experimental verification
Authors: Bacon Christophe , Guilliorit Emmanuel , Hosten Bernard , Chimenti Dale E.
Published: July 2002

The acoustic wave generation in a specimen irradiated by a pulsed microwave is predicted theoretically. The specimen is a viscoelastic rod inserted into a wave guide. The model is based on Maxwell’s equations, heat equation and thermoviscoelasticity theory. Computations show the presence of temperature oscillations due to the electromagnetic interferences in the irradiated rod if its electromagnetic absorption is low. An experimental method to infer indirectly the detailed behavior of microwave-generated acoustic waves in polymer rods, including the influence of electromagnetic wave reflection at the rod ends, is presented. The method consists of measuring the oscillations in the particle acceleration detected at the end of the rod that are induced by variations in the polymer rod length. The oscillations are caused by changing electromagnetic standing-wave conditions within the rod. It is found that these oscillations are in agreement in period, amplitude, and phase, with independent values of the complex dielectric constant and complex acoustic slowness of the polyvinyl chloride samples used in the study.
Application of nonlinear adaptive signal processing techniques to blind source separation and interference suppression
Authors: Sibul H. Leon , Roan J. Micheal , Babich A. Gregory
Published: July 2002

In active noise and vibration control it is important to identify independent noise generation mechanism and sources. In all large physical systems only a mixture of noise sources can be observed. The mixture model can be either linear or nonlinear. Recently there has been an explosion of significant research literature on blind deconvolution. In blind deconvolution, the actual mixture model and source signals are not known; however, in the theoretical development it is assumed that sources are statistically independent. In practice, good results have been obtained even if sources are not independent. If the mixture model is linear, statistically independent noise sources can be separated by blind deconvolution techniques that are based on the theory of the independent component analysis (ICA). We implement ICA by a cascade of the linear adaptive algorithm that is based on singular value decomposition (SVD) and a nonlinear algorithm that is based on a radial-basis function (RBF) neural network. A RBF neural network can also approximate the inverse of the nonlinear mixture model. We use a fast RBF updating algorithm for adaptation of the nonlinear network. Theoretical results are illustrated by computer simulations. Results are compared with linear adaptive signal processing algorithms. [This research has been supported by ONR, Dr. Kam Ng, Program Officer.]
Peak C-weighted sound-pressure level
Authors: Takinami Hiroaki
Published: July 2002

Peak sound pressure is the greatest absolute value of the instantaneous sound pressure occurring within a stated time interval. Peak sound-pressure levels are measured without exponential time weighting and hence are fundamentally different from maximum sound levels measured with time weighting F or S. Until the development of the new International Standard for sound-level meters in IEC 61672, there was no internationally accepted specification for measurements of the peak level of nonsteady or transient sounds. For short-duration sounds, the value of the peak sound-pressure level depends on the frequency bandwidth of the measuring device; very short-duration signals require a wide bandwidth of uniform frequency response. To permit reproducible measurements of various short-duration sounds, IEC 61672 provides specifications for peak C-weighted sound-pressure levels. Frequency-weighting C has the most uniform response over the widest bandwidth of any internationally standarized frequency weighting. The specification requires that the peak C-weighted levels of a single cycle at 31,5 Hz, 500 Hz, and 8 kHz and positive and negative half cycles of 500-Hz sinusoidal signals be measured within practical tolerance limits. Data will be shown to demonstrate conformance of instruments to the specification.
Vibrational patterns and frequency responses of the free plates and box of a violin obtained by finite element analysis
Authors: Bretos J. , Santamarı́a C. , Moral J. Alonso
Published: July 2002

By means of the finite-element method, a study of the vibrational behavior of the violin has been developed in two parts. In the first part, the analysis concerns the free violin plates and their tuning process, which has been accurately described by this numerical tool. In the second part, the whole violin box—except for the neck—has been modeled and its first ten eigenmodes have been calculated. In both parts, the calculated vibrational patterns and frequency responses have been compared with experimental measurements of other researchers.
Low-frequency slow-wave dispersion computations by compound-matrix propagation
Authors: Ivansson Sven
Published: July 2002

Slow P-SV modes whose horizontal slowness tends to infinity while the horizontal wave number tends to zero, as the frequency tends to zero, exist in certain laterally homogeneous fluid-solid media. These modes can be characterized by an asymptotic analysis of the dispersion function. Only certain powers of frequency are possible for the asymptotic increase of the horizontal slowness as the frequency tends to zero: −1/3, −1/2, −3/5, and −2/3. In order to investigate the accuracy of the asymptotic predictions, dispersion-curve computations by propagator techniques are attempted for media composed of homogeneous fluid and solid layers. However, numerical precision is lost by cancellation effects for the elements of the solid-layer compound-matrix propagators that are involved. Guided by the asymptotic growth of these compound-matrix elements, cancellation-free expressions are derived for applications to the slow modes at very low frequencies. The harmful contributions causing loss of numerical precision are eliminated analytically. To demonstrate the success, a numerical case study is performed leading to conjectures about the next-to-leading terms in low-frequency asymptotic expansions of the slow-mode modal slownesses.
Efficacy of melatonin in term neonatal models of perinatal hypoxia‐ischaemia
Authors: Pang Raymand , Han Hyun Jee , Meehan Christopher , Golay Xavier , Miller Suzanne L. , Robertson Nicola J.
Published: April 2022

Objective

Neonatal encephalopathy (NE) is an important cause of mortality and disability worldwide. Therapeutic hypothermia (HT) is an effective therapy, however not all babies benefit. Novel agents are urgently needed to improve outcomes. Melatonin in preclinical studies has promising neuroprotective properties. This meta‐analysis assessed the efficacy of melatonin in term animal models of NE on cerebral infarct size, neurobehavioural tests and cell death.

Methods

A literature search was carried out using Embase, MEDLINE and Web of Science (31 May 2021). We identified 14 studies and performed a meta‐analysis with a random effects model using standardised mean difference (SMD) as the effect size. The risk of bias was assessed using the Systematic Review Centre for Laboratory animal Experimentation tool and publication bias was assessed with funnel plots, and adjusted using trim and fill analysis. Subgroup and meta‐regression analyses were performed to assess the effects of study design variables.

Results

We observed significant reduction in brain infarct size (SMD −2.05, 95% CI [−2.93, −1.16]), improved neurobehavioural outcomes (SMD −0.86, 95% CI [−1.23, −0.53]) and reduction in cell death (SMD −0.60, 95% CI [−1.06, −0.14]) favouring treatment with melatonin. Neuroprotection was evident as a single therapy and combined with HT. Subgroup analysis showed greater efficacy with melatonin given before or immediately after injury and with ethanol excipients. The overall effect size remained robust even after adjustment for publication bias.

Interpretation

These studies demonstrate a significant neuroprotective efficacy of melatonin in term neonatal models of hypoxia‐ischaemia, and suggest melatonin is a strong candidate for translation to clinical trials in babies with moderate–severe NE.
Integrating Additive Manufacturing Techniques to Improve Cell‐Based Implants for the Treatment of Type 1 Diabetes
Authors: Accolla Robert P. , Simmons Amberlyn M. , Stabler Cherie L.
Published: April 2022

The increasing global prevalence of endocrine diseases like type 1 diabetes mellitus (T1DM) elevates the need for cellular replacement approaches, which can potentially enhance therapeutic durability and outcomes. Central to any cell therapy is the design of delivery systems that support cell survival and integration. In T1DM, well‐established fabrication methods have created a wide range of implants, ranging from 3D macro‐scale scaffolds to nano‐scale coatings. These traditional methods, however, are often challenged by their inherent limitations in reproducible and discrete fabrication, particularly when scaling to the clinic. Additive manufacturing (AM) techniques provide a means to address these challenges by delivering improved control over construct geometry and microscale component placement. While still early in development in the context of T1DM cellular transplantation, the integration of AM approaches serves to improve nutrient material transport, vascularization efficiency, and the accuracy of cell, matrix, and local therapeutic placement. This review highlights current methods in T1DM cellular transplantation and the potential of AM approaches to overcome these limitations. In addition, emerging AM technologies and their broader application to cell‐based therapy are discussed.
The short form effort−reward imbalance: Measure of occupational stress for firefighters
Authors: Chin Dal Lae , Kyung MinJung , Li Jian , Phelps Stephanie , Hong OiSaeng
Published: April 2022

Purpose

The original effort−reward imbalance (ERI) questionnaire has been widely used as a measure of occupational stress. The need for brief measurement of psychosocial stress at work has risen. This study examined the psychometric properties of a 16‐item short form ERI (S‐ERI) questionnaire.

Methods

A cross‐sectional study was conducted with a convenience sample of 247 career firefighters in the United States. An internet‐based survey contained the S‐ERI questionnaire, and assessed perceived health, demographics, and work characteristics. Internal consistency was tested by item‐total correlation and Cronbach's α coefficients. Factorial validity was assessed by confirmatory factor analysis (CFA), and criterion validity was examined by testing the S‐ERI's association with perceived health, controlling for other factors.

Results

The study participants were primarily young and mid‐aged White males (mean age = 42 years, 75% White non‐Hispanic, 93% males). The S‐ERI questionnaire showed satisfactory internal consistency, with Cronbach α coefficients above 0.80 for all three scales: effort 0.82, reward 0.83, and overcommitment 0.81. CFA showed all the S‐ERI components had a good fit (goodness‐of‐fit index = 0.99, comparative fit index = 0.92, root mean square error of approximation = 0.06). In terms of criterion validity, significantly increased odds ratios (ORs) for perceived health (those indicating they were less healthy) were found in firefighters in the lowest tertile of reward (OR = 7.06, 95% confidence interval [CI]: 2.86−17.43), and highest tertile of overcommitment (OR = 2.29, 95% CI: 1.00−5.22), after controlling for other factors.

Conclusion

The S‐ERI questionnaire is a reliable and valid measure to assess occupational stress. We recommend the use of S‐ERI as a measure of occupational stress when initiating efforts to improve firefighters' wellness.
Heavy Atom‐Free, Mitochondria‐Targeted, and Activatable Photosensitizers for Photodynamic Therapy with Real‐Time In‐Situ Therapeutic Monitoring
Authors: Miao Junfeng , Huo Yingying , Yao Guangxiao , Feng Yu , Weng Jiajin , Zhao Wei , Guo Wei
Published: April 2022

Based on spin‐orbit charge transfer intersystem crossing mechanism, two heavy‐atom‐free photosensitizers (PSs) BDP1/BDP2 with absorption maxima at 506 nm/660 nm were constructed for photodynamic therapy (PDT). The long triplet state lifetimes and large singlet oxygen quantum yields, coupled with the mitochondria‐targeted feature, made them highly phototoxic toward cancer cells. Moreover, the PDT‐promoted cell apoptosis could be monitored by an obvious fluorescence off‐on response of the two PSs due to the concomitant activation of extensive mitophagy, thus facilitating timely therapeutic feedback to avoid under‐ or over‐treatment. Importantly, such design allows the activatable PSs Glu‐BDP1/Glu‐BDP2 to be fabricated by attaching γ‐glutamyl, a substrate of γ‐glutamyltranspeptidase, to the alkoxyaniline unit of BDP1/BDP2, and their ability in either selectively killing cancer cells over normal cells or in ablating implanted tumour without damage to healthy tissue was demonstrated.
Well‐Controlled Living Polymerization of Phenylacetylenes in Water: Synthesis of Water‐Soluble Stereoregular Telechelic Poly(phenylacetylene)s
Authors: Echizen Kensuke , Taniguchi Tsuyoshi , Nishimura Tatsuya , Maeda Katsuhiro
Published: April 2022

Well‐controlled living polymerization of water‐soluble phenylacetylene derivatives in water was achieved for the first time using a multicomponent catalytic system consisting of [Rh(nbd)Cl]2, an aryl boronic acid, diphenylacetylene having carboxy groups, a tetraalkylammonium hydroxide, and a water‐soluble triphenylphosphine. This catalytic system enables a direct synthesis of various water‐soluble cis‐stereoregular poly(phenylacetylene)s having a narrow molecular weight distribution, the molecular weight of which can be controlled by the initial feed ratio of the monomer to the catalyst. Moreover, the syntheses of water‐soluble telechelic poly(phenylacetylene)s having various functional groups at both chain ends as well as a water‐soluble block copolymer were achieved.
Controlled Tetradeuteration of Straight‐Chain Fatty Acids: Synthesis, Application, and Insight into the Metabolism of Oxidized Linoleic Acid
Authors: Watanabe Ayako , Hama Kotaro , Watanabe Kohei , Fujiwara Yuko , Yokoyama Kazuaki , Murata Shigeo , Takita Ryo
Published: April 2022

We describe a concise and reliable protocol for the precisely controlled tetradeuteration of straight‐chain fatty acids (FAs) at the α‐ and β‐positions that is generally applicable to a variety of FAs, including trans‐FAs, polyunsaturated FAs (PUFAs), and their oxidized derivatives. The precisely controlled introduction of four deuterium atoms into the FAs enables their persistent and quantitative tracking by LC‐MS/MS analysis based on their molecular structures. In addition, the phosphatidylcholine (PC) species prepared from the tetradeuterated FAs thus obtained give a diagnostic peak, namely, a phosphocholine fragment that contains deuterium, in the LC‐MS/MS analysis. With these features, the metabolism of a representative oxidized linoleic acid, that is, hydroxyoctadecadienoic acid (HODE), was investigated, leading to the identification of acyltransferases that transfer the acyl moiety derived from HODE to lysophosphatidylcholine.
Lattice‐Confined Single‐Atom Fe1Sx on Mesoporous TiO2 for Boosting Ambient Electrocatalytic N2 Reduction Reaction
Authors: Chen Jiayin , Kang Yikun , Zhang Wei , Zhang Zhenghao , Chen Yan , Yang Yi , Duan Linlin , Li Yefei , Li Wei
Published: April 2022

Mimicking natural nitrogenase to create highly efficient single‐atom catalysts (SACs) for ambient N2 fixation is highly desired, but still challenging. Herein, S‐coordinated Fe SACs on mesoporous TiO2 have been constructed by a lattice‐confined strategy. The extended X‐ray absorption fine structure and X‐ray photoelectron spectroscopy spectra demonstrate that Fe atoms are anchored in TiO2 lattice via the FeS2O2 coordination configuration. Theoretical calculations reveal that FeS2O2 sites are the active centers for electrocatalytic nitrogen reduction reaction (NRR). Moreover, the finite element analysis shows that confinement of opened and ordered mesopores can facilitate the mass transport and offer an enlarged active surface area for NRR. As a result, this catalyst delivers a favorable NH3 yield rate of 18.3 μg h−1 mgcat.−1 with a high Faradaic efficiency of 17.3 % at −0.20 V versus a reversible hydrogen electrode. Most importantly, this lattice‐confined strategy is universal and can also be applied to Ni1Sx@TiO2, Co1Sx@TiO2, Mo1Sx@TiO2, and Cu1Sx@TiO2 SACs. Our study provides new hints for the design and biomimetic synthesis of highly efficient NRR electrocatalysts.
A rare example of the in situ formation of palladium nanoparticles: The emergence of catalytically active palladium nanoparticles from Pd (II) phosphine complexes in the Suzuki–Miyaura coupling reaction
Authors: Altan Orhan
Published: April 2022

Suzuki–Miyaura coupling (SMC) reactions are one of the most promising routes for carbon–carbon bond formation. It is believed that metal complexes, particularly palladium complexes, are the most effective catalysts for this purpose. However, the catalysis nature whether it is homogenous or heterogeneous is under debate. It is commonly believed that a homogenous catalysis pathway is responsible for the catalytic activity when the phosphine ligands are present in the structure due to the strong phosphorus‐metal interactions. In this study, Pd (II) complexes of phosphino‐benzaldoxime ligands were synthesized, characterized, and tested in SMC reactions. Interestingly, it was found that the catalytic activity increased by 11 times when the amount of catalyst was reduced by 10‐fold and increased by five times when the amount of catalyst was decreased by 100‐fold. The detailed analyses revealed that the palladium nanoparticles (NPs) are responsible for the catalytic activity which was formed in the reaction medium. A plausible mechanism was proposed for the formation of Pd NPs from palladium phosphino‐benzaldoxime complexes in the reaction medium. This study is expected to contribute to the debate over whether the catalytic activity of phosphine‐palladium complexes in SMC reactions results from a homogeneous or heterogeneous pathway.