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Biomedical subjects

D B Huang

Publications and source records attributed to D B Huang.

At least 37 records · Page 2Linked to original sources
PubMed1999

Laboratory measurement of aggression in high school age athletes: provocation in a nonsporting context.

This study investigated the relationship between aggression and type of sports involvement in high school age boys. Athletes (16 boys), ages 15 to 18 years, were separated into two groups, one of 8 athletes who participated in sports with high physical contact, e.g., football and basketball, and the other of 8 athletes who participated in low contact sports, e.g., track and baseball. Students participated in six 25-min. Point Subtraction Aggression Paradigm sessions. The paradigm is an established laboratory model of aggression with three response options: (1) a point-maintained response, (2) an aggressive response, and (3) an escape response. Analysis indicated that the only difference between the groups was that individuals who participated in high contact sports emitted significantly more aggressive responses than individuals who participated in low contact sports. Similarly, psychometric measures of aggression indicated that individuals in the former group self-reported more behavioral incidents of aggression than those in the latter group.

Adolescent↗
PubMed1999

An unusual presentation of constriction band syndrome.

Congenital constriction band syndrome is a rare entity with a wide spectrum of associated congenital anomalies. Review of the pathogenesis and an unusual case of constriction band syndrome in a newborn are presented. Surgical excision of the deformity and the band was performed within the first week of life. There were no vascular or neural structures within the excised tissue, and there were no other associated anomalies other than dextrocardia and an equinovarus deformity of the foot. The wound was closed primarily without the need for Z-plasties. This alternative method of treatment can be considered in such unusual locations of constriction band syndromes.

Amniotic Band Syndrome↗
PubMed1998

The crystal structure of the IkappaBalpha/NF-kappaB complex reveals mechanisms of NF-kappaB inactivation.

IkappaBalpha regulates the transcription factor NF-kappaB through the formation of stable IkappaBalpha/NF-kappaB complexes. Prior to induction, IkappaBalpha retains NF-kappaB in the cytoplasm until the NF-kappaB activation signal is received. After activation, NF-kappaB is removed from gene promoters through association with nuclear IkappaBalpha, restoring the preinduction state. The 2.3 A crystal structure of IkappaBalpha in complex with the NF-kappaB p50/p65 heterodimer reveals mechanisms of these inhibitory activities. The presence of IkappaBalpha allows large en bloc movement of the NF-kappaB p65 subunit amino-terminal domain. This conformational change induces allosteric inhibition of NF-kappaB DNA binding. Amino acid residues immediately preceding the nuclear localization signals of both NF-kappaB p50 and p65 subunits are tethered to the IkappaBalpha amino-terminal ankyrin repeats, impeding NF-kappaB from nuclear import machinery recognition.

Amino Acid Sequence↗
PubMed1998

A domain flip as a result of a single amino-acid substitution.

BACKGROUND: The self-assembly properties of beta domains are important features of diverse classes of proteins that include cell-adhesion molecules, surface receptors and the immunoglobulin superfamily. Immunoglobulin light-chain variable domains are well suited to the study of structural factors that determine dimerization, including how residues at the interface influence the preferred dimer arrangement. RESULTS: Single-site mutants of light-chain variable domain Len, designated LenQ38E and LenK30T, formed 'flipped' dimers in which one domain was rotated by about 180 degrees compared with the native protein. The dimer in the native protein is similar to that found between variable domains in Fab immunoglobulin fragments. When compared to the native dimer, more surface area is buried, and more hydrogen bonds and salt bridges are formed between the monomers in the flipped conformation. CONCLUSIONS: Immunoglobulin light-chain variable domains can form a minimum of two distinct quaternary structures. Single-site mutations resulting from changes of one base, such as the exchange of Gln38 to Glu or Lys30 to Thr, change the 'conventional' dimer of protein Len to a flipped arrangement. Native Len is not found in the flipped-domain dimer conformation because it would have excess positive electrostatic potential at the dimer interface that is not compensated by other forces. Excess negative or positive electrostatic potential at the dimer interface can have a determining effect on the mode of dimerization.

Crystallography, X-Ray↗
PubMed1998

Crystal structure of p50/p65 heterodimer of transcription factor NF-kappaB bound to DNA.

The NF-kappaB p50/p65 heterodimer is the classical member of the Rel family of transcription factors which regulate diverse cellular functions such as immune response, cell growth, and development. Other mammalian Rel family members, including the proteins p52, proto-oncoprotein c-Rel, and RelB, all have amino-terminal Rel-homology regions (RHRs). The RHR is responsible for the dimerization, DNA binding and cytosolic localization of these proteins by virtue of complex formation with inhibitor kappaB proteins. Signal-induced removal of kappaB inhibitors allows translocation of dimers to the cell nucleus and transcriptional regulation of kappaB DNA-containing genes. NF-kappaB specifically recognizes kappaB DNA elements with a consensus sequence of 5'-GGGRNYYYCC-3' (R is an unspecified purine; Y is an unspecified pyrimidine; and N is any nucleotide). Here we report the crystal structure at 2.9 A resolution of the p50/p65 heterodimer bound to the kappaB DNA of the intronic enhancer of the immunoglobulin light-chain gene. Our structure reveals a 5-base-pair 5' subsite for p50, and a 4-base-pair 3' subsite for p65. This structure indicates why the p50/p65 heterodimer interface is stronger than that of either homodimer. A comparison of this structure with those of other Rel dimers reveals that both subunits adopt variable conformations in a DNA-sequence-dependent manner. Our results explain the different behaviour of the p50/p65 heterodimer with heterologous promoters.

Amino Acid Sequence↗
PubMed1997

The role of DNA in the mechanism of NFkappaB dimer formation: crystal structures of the dimerization domains of the p50 and p65 subunits.

BACKGROUND: Members of the rel/NFkappaB family of transcription factors play a vital role in the regulation of rapid cellular responses, such as those required to fight infection or react to cellular stress. Members of this family of proteins form homo- and heterodimers with differing affinities for dimerization. They share a structural motif known as the rel homology region (RHR), the C-terminal one third of which mediates protein dimerization. Crystal structures of the rel/NFkappaB family members p50 and p65 in their DNA-bound homodimeric form have been solved. These structures showed that the residues from the dimerization domains of both p50 and p65 participate in DNA binding and that the DNA-protein and protein dimerization surfaces form one continuous overlapping interface. We desired to investigate the contribution of DNA to NFkappaB dimerization and to identify the mechanism for the selective association of rel/NFkappaB family peptides into transcriptionally active dimers. RESULTS: We report here the crystal structures of the dimerization domains of murine p50 and p65 at 2.2 A and 2.0 A resolution, respectively. A comparison of these two structures suggests that conservative amino acid changes at three positions are responsible for the differences in their dimer interfaces. The presence of the target DNA does not change the dimer interface of either protein in any significant manner. CONCLUSIONS: These two structures suggest that the rel/NFkappaB family of transcription factors use only a few conservative changes in their amino acid sequences to form a host of dimers with varying affinities for dimerization. Amino acids at positions corresponding to 254, 267, and 307 of murine p50, function as primary determinants for the observed differences in dimerization affinity. The DNA-contacting charged amino acid sidechains from the dimerization domains are held in a similar conformation in both the DNA-bound and free states, therefore, no major structural rearrangement is required to bring these residues into contact with the DNA.

Amino Acid Sequence↗
PubMed1997

Variable domain structure of kappaIV human light chain Len: high homology to the murine light chain McPC603.

Antibody light chains of the kappa subgroup are the predominant light chain component in human immune responses and are used almost exclusively in the antibody repertoire of mice. Human kappa light chains comprise four subgroups. To date, all crystallographic studies of human kappa light chains were carried out on proteins of the kappaI subgroup. The light chain produced by multiple myeloma patient Len. was of the kappaIV subgroup, it differed by only one residue from the germ-line gene encoded protein. The variable domain fragment of the light chain was crystallized from ammonium sulfate in space group C222(1). The crystal structure was determined by molecular replacement and refined at 1.95 A resolution to an R-factor of 0.15. Protein Len has six additional residues in its CDR1 segment compared to the kappaI proteins previously characterized. The kappaIV variable domain, Len, differs in only 23 of 113 residues from murine kappa light chain McPC603. The RMS deviation upon superimposing their alpha-carbons was 0.69 A. The CDR1 segment of the human and murine variable domains have the same length and conformation although their amino acid sequences differ in 5 out of 17 residues. Structural features were identified that could account for the significantly higher stability of the human kappaIV protein relative to its murine counterpart. This human kappaIV light chain structure is the closest human homolog to a murine light chain and can be expected to facilitate detailed structural comparisons necessary for effective humanization of murine antibodies.

Amino Acid Sequence↗
PubMed1997

Molecular modeling of immunoglobulin light chains implicates hydrophobic residues in non-amyloid light chain deposition disease.

Light chain deposition disease is a severe complication of certain immunoproliferative disorders, due to the secretion of a monoclonal light chain which precipitates close to basement membranes of several tissues. A kappa isotype restriction and an unusual frequency of a variable region subgroup (VkappaIV) suggest that precise structural features govern the propensity of pathogenic light chains to precipitate in extracellular spaces. We studied primary structures of light chains from six patients with light chain deposition disease in comparison with light chains from other pathological conditions. Sequence alignment revealed the presence of certain amino acids only in light chain deposition disease, in particular non-polar replacing hydrophilic residues. To determine the role of these residues, structures of the variable domain from four kappa chains belonging to VkappaI and VkappaIV subgroups responsible for deposition disease were modeled using known immunoglobulins as templates. The most evident structural features shared by all pathogenic light chains were hydrophobic residues exposed to the solvent in complementarity determining regions 1 or 3. In contrast to immunoglobulin light chain-related amyloidosis, where deposition of organized material might be due to electrostatic interactions between light chain dimers, hydrophobic interactions could enhance amorphous precipitation in non-amyloid light chain deposition disease.

Amino Acid Sequence↗
PubMed1996

Pitfalls of molecular replacement: the structure determination of an immunoglobulin light-chain dimer.

The structure of protein Cle, a human light-chain dimer from the lambdaIII subgroup, was determined using 2.6 A data; the R value is 18.4%. The structure was solved, after a false start, by molecular replacement with the lambdaII/V Mcg protein as a search structure. When the refinement did not proceed beyond an R value of 27%, it was discovered that while the constant domains were in their correct positions in the unit cell, the incorrect variable domains were used for defining the molecule. The correct solution required a rotation of 180 degrees around the local twofold axis that relates the two constant domains of the dimer. The correct variable domain positions overlap about 70% of the same volume as the incorrect ones of a symmetry-related molecule. The refinement distorted the geometries of the domains. Though the constant domains were in their correct positions, the r.m.s. (root-mean-square) deviation of the Calpha atom position was 1.2 A when the two constant domains were compared. For the correct structure, this value is 0.5 A. The phi and psi angles, the r.m.s. chiral value and the free R value, even when calculated a posteriori, were good indicators of the correctness of the structure. The quaternary structure of the Cle molecule is similar to that in Mcg (crystallized from ammonium sulfate); the elbow bend is 115 degrees. However, the arrangement of the variable domains differs from that observed in other variable domain dimers. The variable domains of Cle are 0.7 A closer than in Mcg or variable dimer Rei. The hydrogen bonding at the interface of the two domains is novel. Residues Tyr36 from both monomers form a hydrogen bond that is part of a network with the Gln89 residues from both monomers. For the first time hydrogen bonds were observed between the main-chain peptide N and O atoms of the complementarity-determining region CDR2 and CDR3 segments of both monomers.

Journal Article↗
PubMed1996

Three quaternary structures for a single protein.

The structure of a multisubunit protein (immunoglobulin light chain) was solved in three crystal forms, differing only in the solvent of crystallization. The three structures were obtained at high ionic strength and low pH, high ionic strength and high pH, and low ionic strength and neutral pH. The three resulting "snapshots" of possible structures show that their variable-domain interactions differ, reflecting their stabilities under specific solvent conditions. In the three crystal forms, the variable domains had different rotational and translational relationships, whereas no alteration of the constant domains was found. The critical residues involved in the observed effect of the solvent are tryptophans and histidines located between the two variable domains in the dimeric structure. Tryptophan residues are commonly found in interfaces between proteins and their subunits, and histidines have been implicated in pH-dependent conformation changes. The quaternary structure observed for a multisubunit protein or protein complex in a crystal may be influenced by the interactions of the constituents within the molecule or complex and/or by crystal packing interactions. The comparison of buried surface areas and hydrogen bonds between the domains forming the molecule and between the molecules forming the crystals suggest that, for this system, the interactions within the molecule are most likely the determining factors.

Ammonium Sulfate↗
PubMed1996

[Clinical summary of relatively large dose of sodium morrhuate injection for the treatment of maxillofacial cavernous hemangionma:A report of 764 cases]

The result of relatively large dose of 5% sodium morrhuate injection(SIM) for the treatment of 764 cases in the cavernous hemangioma in orofacial region is presented.The curative rate was improved,Its cure and elementary cure rate were 89.27%.The dosage,course and practical approach were discussed,The relationship of factors listed above with the curative effect were mentioned.The reaction and complications might be influencing the recurrence rate.Hemangioma after SMI should be observed in order to consolidate its curative effect.

Journal Article↗
PubMed1994

Comparison of crystal structures of two homologous proteins: structural origin of altered domain interactions in immunoglobulin light-chain dimers.

The sequence and structure of a second human kappa 1 immunoglobulin light-chain variable domain, Wat, has been determined. The R-factor is 15.7% for 1.9-A data. One hundred and ninety-five water molecules were identified; 30 water molecules were located in identical positions in each of the monomers. Some of the water molecules are integral parts of the domains. This light chain is encoded by the same variable domain gene that encoded the previously characterized kappa I variable domain, Rei. Due to limited somatic mutation, the two highly homologous proteins differ in only 20 of the 108 residues. Wat crystallized in space group P6(4) while Rei crystallized in space group P6(1); in both crystals, the asymmetric unit was the noncovalent dimer. Although the basic domain structure is the same for both proteins, the relative positions of the domains within the two dimers differ. This difference is most likely accounted for by the replacement of Tyr36 in Rei by Phe in the Wat protein. Residue Tyr36 is part of the hydrogen-bonding network in the interface between the domains in Rei. Losing the hydrogen-bonding capability of residue 36 by replacement of Tyr by Phe alters the network of hydrogen bonds between the domains, resulting in a different domain-domain contact. The details of lattice contacts in the two crystals were compared. One type of contact that extends the beta-sheet of the individual domains was conserved, but because it involved different symmetry elements within the crystal, different crystal packing resulted. In the Wat crystal, one of the contacts shows an example of how a symmetrical binding site can "bind" an asymmetrical object. Further, the examination of the Wat crystal also illustrates how the different crystalline environments of the domains of the dimer results in different distributions of temperature factors for the residues within the domains.

Amino Acid Sequence↗
PubMed1993

The tetrasaccharide nystose trihydrate: crystal structure analysis and hydrogen bonding.

The crystal structure of nystose trihydrate, O-beta-D-fructofuranosyl-(2-->1)-O-beta-D-fructofuranosyl-(2-->1)-beta-D -fructofuranosyl alpha-D-glucopyranoside trihydrate, C24H42O21.3H2O, has been determined using Cu K alpha X-ray data at 121 K. The space group is P2(1)2(1)2(1), with 4 molecules in a unit cell of dimensions a = 10.155(1), b = 13.506(1), and c = 23.278(2) A. The structure was refined to R = 0.052 and RW = 0.048 for 2734 observed structure amplitudes. The alpha-D-glucopyranose unit of the molecule has the normal 4C1 chair conformation and the three fructofuranose units have twist conformations lying between E3 and 4T5. One of the three water molecules is distributed over two sites: W-3 with occupancy 0.80 and W-3' with occupancy 0.20. All the hydrogen atoms were located on the difference synthesis with the exception of those attached to the low-occupancy water site. All hydroxyls, two of the three linkage oxygen atoms, and the water molecules are involved in a complex three-dimensional network which can be decomposed into a series of infinite chains intersecting at the water molecules to form homo- and hetero-dromic cycles.

Carbohydrate Conformation↗
PubMed1993

[New techniques of cultivating Ganoderma lucidum (W. Curt.:Fr)Karst.,Rev. with woodlog].

Imitating wild cultivation of Ganoderma lucidum with short-woodlog is a method of cultivating artificial G. lucidum developed in recent years. The method can be applied to large scale production. This paper shows that section-inoculating and impregnating with steamed shortwoodlog indoors and soil-cover cultivating under large shed are important in the cultivation.

Methods↗
PubMed1992

Crystal structure and n.m.r. analysis of lactulose trihydrate.

The 13C CPMAS n.m.r. spectrum of 4-O-beta-D-galactopyranosyl-D-fructose (lactulose) trihydrate, C12H22O11.3 H2O, identifies the isomer in the crystals as the beta-furanose. This is confirmed by a crystal structure analysis, using CuK alpha X-ray data at room temperature. The space group is P212121, with Z = 4 and cell dimensions a = 9.6251(3), b = 12.8096(3), c = 17.7563(4) A. The structure was refined to R = 0.031 and Rw 0.025 for 1929 observed structure amplitudes. All the hydrogen atoms were unambigously located on difference syntheses. The conformation of the pyranose ring is the normal 4C1 chair and that of the furanose ring is 4T3. The 1----4 linkage torsion angles are O-5'-C-1'-O-1'-C-4 = 79.9(2) degrees and C-1'-O-1'-C-4-C-5 = -170.3(2) degrees. All hydroxyls, ring and glycosidic oxygens, and water molecules are involved in the hydrogen bonding, which consists of infinite chains linked together by water molecules to form a three-dimensional network. There is a three-centered intramolecular, interresidue hydrogen bond from O-3-H to O-5' and O-6'. The n.m.r. spectrum of the amorphous, dehydrated trihydrate suggests the occurrence of a solid-state reaction forming the same isomeric mixture as was observed in crystalline anhydrous lactulose, although the mutarotation of the trihydrate when dissolved in Me2SO is very slow.

Carbohydrate Conformation↗
PubMed1992

The crystal structure of D-threitol at 119 K and 198 K.

A sample of DL-threitol, C4H10O4 (Sigma Chemical Co.), on recrystallization provided crystals of D- and L-threitol. The crystal structure was determined at 119 K and 298 K. The space group of D-threitol is P3(1)21, with three molecules in a unit cell at 119 K [298 K] of a = 10.0995(5) [10.1405(8)], c = 4.8407(4) [4.8767(4)] A. The final agreement R-factor was 0.050 for 302 intensities [0.069 for 244 intensities]. The molecules have the straight carbon-chain conformation with twofold axial symmetry. The hydroxyl groups are hydrogen bonded in infinite chains extending in the direction of the threefold screw axis. One of the hydroxyl hydrogens is twofold disordered, so that alternate chains have reversed donor-acceptor directions.

Carbohydrate Conformation↗
PubMed1991

Hydrogen bonding in the crystal structure of alpha,beta-panose.

The crystal structure of panose, O-alpha-D-glucopyranosyl-(1----6)-O-alpha-D-glucopyranosyl-(1----4)-D-gl ucose, C18H32O16, has been refined using low-temperature, 123 K, CuK alpha X-ray data. Difference syntheses and least-squares refinement showed a 16% substitution of alpha-panose by the beta anomer. All the hydrogen atoms were located on difference synthesis with the exception of one attached to the low occupancy (beta) O-1". The final R-factor was 0.036 for 2135 observed structure amplitudes. The molecular conformation is stabilized by two interresidue intramolecular hydrogen bonds. All the hydroxyls and glycosidic oxygen atoms are involved in the hydrogen bonding, which is a two-dimensional network formed from finite and infinite chains.

Carbohydrate Conformation↗