The crystal structures of polybis(μ
2
-4,4′-bipyridine
N
,
N
′-dioxide-κ
2
O
:
O′
)trinitratocerium(III) and its isostructural praseodymium and neodymium analogues feature a 4
4
grid-like layered ...structure with interdigitation of layers promoted by C—H⋯O interactions between nitrate anions and 4,4′-bipyridine
N
,
N
′-dioxide ligands.
Three isostructural coordination networks of Ce, Pr, and Nd nitrate with 4,4′-bipyridine
N
,
N
′-dioxide (bpydo) are reported, namely polytris(nitrato-κ
2
O
,
O
′)cerium(III)-bis(μ
2
-4,4′-bipyridine
N
,
N
′-dioxide-κ
2
N
:
N
′), Ce(NO
3
)
3
(C
10
H
8
N
2
O
2
)
2
, polytris(nitrato-κ
2
O
,
O
′)praeseodymium(III)-bis(μ
2
-4,4′-bipyridine
N
,
N
′-dioxide-κ
2
N
:
N
′), Pr(NO
3
)
3
(C
10
H
8
N
2
O
2
)
2
, and polytris(nitrato-κ
2
O
,
O
′)neodymium(III)-bis(μ
2
-4,4′-bipyridine
N
,
N
′-dioxide-κ
2
N
:
N
′, Nd(NO
3
)
3
(C
10
H
8
N
2
O
2
)
2
. All three compounds are isostructural to the previously reported La analogue. The asymmetric unit of
Ln
(NO
3
)
3
(μ
2
-bpydo)
2
contains one lanthanide cation, two bpydo ligands, and three nitrate anions. Both bpydo ligands act as end-to-end μ
2
-bridges and display nearly ideal
cis
and
gauche
conformations, respectively. The bpydo ligands link the ten-coordinate
Ln
III
cations, forming interdigitating 4
4
grid-like layers extending parallel to (-101), where interdigitation of layers is promoted by C—H⋯O interactions between nitrate anions and bpydo ligands. The interdigitated layers are linked to sets of neighboring layers
via
further C—H⋯O and π–π interactions.
In order to improve the genetic characterisation of the barnacle Balanus amphitrite, normalised EST libraries for the developmental stages, viz. nauplius (a mix of instars I and II), cyprid and ...adult, were generated. The libraries were sequenced independently using 454 technologies and 575,666 reads were generated. For adults, 4843 unique isotigs were estimated and 6754 and 7506 in the cyprid and naupliar stage, respectively. It was found that some of the previously proposed cyprid-specific bcs genes were also expressed during the naupliar and adult stage. Furthermore, as lectins have been hypothesised to influence settlement cue recognition in barnacles, the database was searched for lectin-like isotigs. Two proteins, uniquely expressed in either the cyprid or the adult stage, matched a mannose receptor, and their nucleotide sequences were 33% and 31% identical to a lectin (BRA-3) isolated from Megabalanus rosa. Further characterisation of these genes may suggest their involvement in settlement.
The killer cell Ig-like receptors (KIR) of natural killer (NK) cells recognize major histocompatibility complex (MHC) class I ligands and function in placental reproduction and immune defense against ...pathogens. During the evolution of monkeys, great apes and humans, an ancestral
KIR3DL
gene expanded to become a diverse and rapidly evolving gene family of four
KIR
lineages. Characterising the
KIR
locus are three framework regions, defining two intervals of variable gene-content. By analysis of four
KIR
haplotypes from two species of gibbon, we find that the smaller apes do not conform to these rules. Although diverse and irregular in structure, the gibbon haplotypes are unusually small, containing only two to five functional genes. Comparison with the predicted ancestral hominoid
KIR
haplotype indicates that modern gibbon
KIR
haplotypes were formed by a series of deletion events, which created new hybrid genes as well as eliminating ancestral genes. Of the three framework regions, only
KIR3DL3
(lineage V), defining the 5’ end of the
KIR
locus, is present and intact on all gibbon
KIR
haplotypes.
KIR2DL4
(lineage I) defining the central framework region has been a major target for elimination or inactivation, correlating with the absence of its putative ligand, MHC-G, in gibbons. Similarly, the MHC-C driven expansion of lineage III
KIR
genes in great apes has not occurred in gibbons because they lack MHC-C. Our results indicate that the selective forces shaping the size and organisation of the gibbon
KIR
locus differed from those acting upon the
KIR
of other hominoid species.
Cross‐resistance between different classes of anti‐neoplastic agents can jeopardize successful combination cancer chemotherapy. In this study, we observed an unexpected cross‐resistance between the ...podophyllotoxine derivative etoposide (VP) and the nucleoside analogue cladribine (CdA) in CCRF‐CEM cells developed for resistance to VP. The resistant cells also displayed 14‐ and twofold resistance to cytarabine (ara‐C) and gemcitabine respectively. Closer analysis of these cells showed that they contained lower amounts of topoisomerase (topo) IIα (P < 0·001) and β protein (P < 0·026), formed substantially lower amounts of the topo II–DNA complex, and had a markedly decreased level of Fas (CD95/APO‐1)‐ligand mRNA expression. Interestingly, Fas expression in the resistant cells did not differ from that in the parental cell line. No differences were observed in the accumulation/efflux of daunorubicin or in the gene expressions of P‐glycoprotein, multidrug resistance‐associated protein and the lung resistance‐related protein. The activity of deoxycytidine kinase (dCK), responsible for activation of CdA and ara‐C, was the same for resistant and wild‐type cells. However, there was an increase in the activity of the cytosolic 5′‐nucleotidases (5′‐NT), responsible for deactivation of nucleotides, amounting to 206% (P < 0·001) for the high Km and 134% (P < 0·331) for the low Km 5′‐NT in resistant cells. The high Km 5′‐NT is probably responsible for the decreased amount of the active metabolite CdA 5′‐triphosphate 40% decreased (P < 0·045), as well as for other purine ribonucleosides and deoxyribonucleosides triphosphates in the resistant cells. In contrast, a significantly higher deoxycytidine triphosphate (dCTP) level (167%, P < 0·001) was observed in the resistant cells. Thus, this study suggests that the major cause of resistance to the nucleoside analogues CdA and ara‐C in cells selected for resistance to VP is a result of metabolic alterations producing increased activity of 5′‐NT and higher dCTP levels. Furthermore, these results indicate that there is a common factor in the regulation of nucleotide‐degrading enzymes and DNA topoisomerases, which may be altered in cross‐resistant cells.
The biochemistry and circadian regulation of luminescence in two Pyrocystis species, P. lunula Hulburt and P. noctiluca Murray et Haeckel, were compared with a well‐studied species, Gonyaulax ...polyedra Stein. All exhibit circadian rhythms and all have similar luciferins and luciferases. However, the Pyrocystis species lack a second protein involved in the reaction in Gonyaulax, the luciferin (substrate) binding protein, which sequesters the luciferin at the cytoplasmic pH and releases it upon acidification, thus controlling the characteristic flashing, which is similar in the three species. More striking is the difference in the circadian regulation of luminescence, which in Gonyaulax involves the daily synthesis and destruction of the two proteins, along with the luminous organelles (scintillons) from which light is emitted, and which are present in all species. In the Pyrocystis species, the amount of luciferase is the same in extracts made during the day and night phases; its circadian regulation in vivo may be attributed to a change in its localization from day to night phase.
Multidrug resistance gene (mdrl) expression is associated with a poor prognosis in acute myelocytic leukaemia (AML). Whether expression of the recently described multidrug resistance-associated gene ...(mrp) has any prognostic importance in AML is still unclear. The aim of the present study was to investigate the functional role of the mdr1 and mrp mRNA levels in peripheral leukaemic cell populations from patients with AML. Peripheral leukaemic cells from 10 patients with AML were incubated with daunorubicin (DNR). Cellular DNR content was analysed with a fluorescence-activated cell sorter (FACS). From each cell population the 20-25% cells with the lowest and highest DNR content were sorted out, and mdr1 and mrp RNA were quantified in these subpopulations with competitive polymerase chain reaction. The ratio between the mean DNR content in the cell populations with high and low DNR content varied between 1.9 and 6.6. the cell fraction with low DNR content had higher (3.8-40 times)mdr1 mRNA levels in 10/10 patients and higher (1.4-26 times) mrp mRNA levels in 8/10, as compared to the cell fraction with high DNR accumulation. In conclusion, mdr1 and mrp mRNA expressions are heterogenous in leukaemic cell populations from patients with AML. The mdr1 expression, and to some extent mrp expression, is inversely correlated to DNR accumulation in vitro.
The title compound, C6H8N2O2, was prepared from 2,5-dimethylpyrazine, acetic acid, and hydrogen peroxide. The 2,5-dimethylpyrazine 1,4-dioxide molecule is located on an inversion center. ...π–π interactions between neighboring 2,5-dimethylpyrazine 1,4-dioxide molecules are observed with an interplanar distance of 3.191 Å. Each 2,5-dimethylpyrazine 1,4-dioxide molecule is linked to four neighboring N-oxide molecules through C—H...O hydrogen-bonding interactions, forming two-dimensional layers.
The title one-dimensional coordination network, {Gd2(NO3)6(C10H8N2O2)3·2CH2Cl2}n, is isostructural with the previously reported Tb and Tl coordination networks and to its Eu analog. The GdIII ...cation is coordinated in a distorted tricapped trigonal-prismatic fashion by nine O atoms from three bridging 4,4′-bipyridine N,N′-dioxide ligands and three chelating nitrate anions. None of the atoms lie on a special position, but there is an inversion center located between the rings of one of the ligands. The network topology is ladder-like, and each ladder interacts with six neighboring ladders through C—H...O hydrogen bonds. The packing motif of the ladders allows for the formation of channels that run parallel to the a axis; these channels are filled with CH2Cl2 solvent molecules that interact with the ladders through C—H...O hydrogen bonds
The title compound, C(6)H(8)N(2)O(2), was prepared from 2,5-dimethyl-pyrazine, acetic acid, and hydrogen peroxide. The 2,5-dimethyl-pyrazine 1,4-dioxide mol-ecule is located on an inversion center. ...π-π inter-actions between neighboring 2,5-dimethyl-pyrazine 1,4-dioxide mol-ecules are observed with an inter-planar distance of 3.191 Å. Each 2,5-dimethyl-pyrazine 1,4-dioxide mol-ecule is linked to four neighboring N-oxide mol-ecules through C-H⋯O hydrogen-bonding inter-actions, forming two-dimensional layers.
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