Studies on the receptors of the MNSs group system.

Results with modified human red cell membrane sialoglycoproteins indicate that alkali-labile sialic acid and amino groups are parts of the erythrocyte receptor sites recognized by common rabbit and human anti-M and -N sera. The "N" antigen, demonstrable in MM glycoprotein preparations by rabbit anti-N, has structural properties which are similar to those of the MN receptors. Sialic acid, amino groups and carbohydrate, susceptible to periodate oxidation, are not involved in the Ss antigen sites. The specificity of the Vicia graminea lectin is dependent on free amino and carboxyl groups. Its affinity for the substances is increased by blocking of amino groups.     

An analysis of the micronuclei in the oral mucosa for assessing the cytogenetic effect of environmental pollutants

The frequencies of micronuclei in the buccal mucosa cells are investigated in several groups: in the control group and in the groups of workers from the pure iron factory (populated area A): in the control group and in the group of workers from the microbiological works (area B). Frequencies of micronuclei are shown to somewhat increase in workers of both works as compared to the control groups. Levels of micronuclei are revealed to increase in the smokers as against the nonsmokers in the group of workers from the microbiological factory. The above examination permits recommending analysis of micronuclei to estimate xenobiotics polluting respiratory tracts.     

Limited validity of group additivity for the folding energetics of the peptide group

The principle of group additivity is a standard feature of analyses of the energetics of protein folding, but it is known that it may not always be valid for the polar peptide group. The neighboring residue effect shows that group additivity is not strictly valid for a heteropeptide. We show here that group additivity fails seriously for peptide groups close to either peptide end, even for a homopeptide that has blocked end groups with no formal charges involved. The failure of group additivity is caused by the electrostatic character of the solvation of peptide polar groups and is illustrated with values of the electrostatic solvation free energy (ESF) calculated by DelPhi. Solvation free energies and enthalpies are known experimentally for monoamides and are often used to model the solvation of peptide groups, but ESF results show that monoamide values are very different from those of peptide groups. A main cause of the difference is that peptide solvation depends on the dipole-dipole interactions made between adjacent peptide groups, which vary with peptide conformation. Ligands that interact with the peptide backbone by an electrostatic mechanism could show a similar peptide end effect, and hydrogen exchange results from the literature confirm that exchange rates are position-dependent close to peptide ends.     

Genetic mapping of the chromosome of the cyanobacterium, Anabaena variabilis. Proximity of the structural genes for nitrogenase and ribulose-bisphosphate carboxylase

A cosmid library of DNA from the chromosome of the nitrogen-fixing cyanobacterium, Anabaena variabilis, has been organized into about 40 linkage groups on the basis of cosmid-cosmid hybridization. Nitrogenase and ribulose-bisphosphate carboxylase are protein complexes that are, respectively, active in heterocysts and absent from vegetative cells, and active in vegetative cells and absent from heterocysts. The structural genes for the proteins of these two complexes are found to be in close proximity within one of the linkage groups. Other genes have also been tentatively localized on the basis of heterologous hybridization. Possible methods for linking the defined linkage groups are discussed.     

中国蒙古族的身高特征

研究目前中国蒙古族主要族群身高情况。对中国蒙古族共13个族群4410例（男43%,女57%）成人身高进行了测量,分析蒙古族身高分型情况,探讨不同年龄组之间、不同族群之间的身高变化趋势。中国蒙古族男性为超中等身材,女性为中等身材。在13个族群中,男性是额济纳土尔扈特部身高最高,云南蒙古族身材最矮。女性是鄂尔多斯部身材最高,云南蒙古族身材最矮。3个年龄组间身高差异均具有统计学意义。男性、女性都以高型出现率最高,过矮型出现率和很高型出现率都很低。中国蒙古族身高与中国其他北方族群接近,高于7个中国南方族群,低于北方汉族,但高于南方汉族,低于日本人、韩国人。中国蒙古族13个族群间身高差异均具有统计学意义,在中国族群中蒙古族属于身材较高的族群。     

On the environment of ionizable groups in globular proteins

The environment of ionizable groups in 36 proteins is characterized in terms of solvent-accessibility, salt-bridge formation and hydrogen-bonding. Possible implications of our results as to the protonation state of buried ionizable groups are considered and patterns useful for model building studies on proteins are derived. The most interesting finding is that there are on average two completely buried ionizable groups per protein of which at least 20% do not form saltbridges. However, all buried ionizable groups form hydrogen bonds with neutral polar groups.     

Multiple hierarchies and the duplex nature of groups

This article examines the links between multiple hierarchies and a wide range of broad-based groups, in order to develop a theoretical framework capable of integrating group phenomena, social identities, and political mobilization. Various case-studies are used to illustrate how hierarchies between and within groups are obfuscated by discrepancies between the material and symbolic aspects of social reality. Yet such discrepancies, which are partly transparent, can generate contestation and the reconfiguration of groups. A duplexity model, which treats groups as a complex mix of embodied categories and observable attributes whose interconnections are contingent, can help unravel crosscutting social cleavages.     

An analysis of the effect of mono- and di-valent cations on the forces between charged lipid membranes with special reference to the grana thylakoids of chloroplasts

A numerical technique is applied to the investigation of salt effects on the electrostatic repulsion between lipid membranes with chargeable anionic groups. It is found that when such groups dissociate easily, the effects of mono- and divalent cations are antagonistic under low salt conditions. However, when the surface anionic groups have pK values closer to the bulk pH value, the effects are much more subtle. The results of the analysis are applied to explain experimental observations on chloroplast grana thylakoid membranes, but they may find more general use.     

Sum frequency vibrational spectroscopy: the molecular origins of the optical second-order nonlinearity of collagen

The molecular origins of second-order nonlinear effects in type I collagen fibrils have been identified with sum-frequency generation vibrational spectroscopy. The dominant contributing molecular groups are: 1), the methylene groups associated with a Fermi resonance between the fundamental symmetric stretch and the bending overtone of methylene; and 2), the carbonyl and peptide groups associated with the amide I band. The noncentrosymmetrically aligned methylene groups are characterized by a distinctive tilt relative to the axis perpendicular to the main axis of the collagen fiber, a conformation producing a strong achiral contribution to the second-order nonlinear effect. In contrast, the stretching vibration of the carbonyl groups associated with the amide I band results in a strong chiral contribution to the optical second-order nonlinear effect. The length scale of these chiral effects ranges from the molecular to the supramolecular.     

Location of two sulfhydryl groups in the rhodopsin molecule by use of the spin label technique.

Sulfhydryl groups of membrane-bound rhodopsin are studied with the spin label technique by using five maleimide derivative probes of different lengths. Two sulfhydryl groups are titrated per molecule of rhodopsin, These groups are located in protected but probably different environments, less than 12 A away from the aqueous phase. A distance of about 37 A is measured between the two groups. These results are consistent with a model in which the two groups would be located close by the external surface of the protein but embedded within the membrane layer, the strong immobilization of the label molecules resulting from phosphlipid-protein interactions.     

Location of two sulfhydryl groups in the rhodopsin molecule by use of the spin label technique

Sulfhydryl groups of membrane-bound rhodopsin are studied with the spin label technique by using five maleimide derivative probes of different lengths. Two sulfhydryl groups are titrated per molecule of rhodopsin. These groups are located in protected but probably different environments, less then 12 Å away from the aqueous phase. A distance of about 37 Å is measured between the two groups. These results are consistent with a model in which the two groups would be located close by the external surface of the protein but embedded within the membrane layer, the strong immobilization of the label molecules resulting from phospholipid-protein interactions.     

Reactions of the sulfhydryl groups of alanyl-tRNA synthetase

The six sulfhydryl groups in each subunit of the alanyl-tRNA synthetase of Escherichia coli react with sulfhydryl reagents with at least four different rates. One reacts very rapidly with 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB), and a second reacts somewhat less rapidly with this reagent. These two groups are required for transfer activity, which is lost in proportion to the extent of derivatization. Two other groups react more slowly, with a consequent loss of exchange activity. The remaining two sulfhydryl groups do not react with DTNB until the protein is denatured. The inactivations are reversed by dithiothreitol. Two sulfhydryl groups react with N-ethylmaleimide (NEM) and with a spin-label derivative of NEM. These reactions resemble the modification of two sulfhydryl groups with DTNB, in that they also inactivate the transfer reaction but not the ATP:PP_i exchange. The two spin labels are incorporated at similar rates but are in very different environments, one highly exposed and one highly immobilized. These groups do not interact with Mn²⁺, which is bound to the enzyme in the absence of ATP.     

Groups of coupled species in the vegetation cover in the landscapes of the basins of the upper and middle courses of the Pechora River as indicators of ecotopic and phytocenotic conditions

Analysis of the intraspecific coupling and use of the graph theory in the vegetation cover of the landscapes of the upper and middle courses of the Pechora River were used to distinguish seven groups of species of vascular plants. With the help of ecological scales of H. Ellenberg and participation coefficient of V. S. Ipatov we showed that these groups occupy different positions in the ecological space and are characterized by clear cenotic role in certain vegetation communities. The Pleiades of coupled species, the majority of which are interpreted as ecological-cenotic groups of species, can be used as indicators of eco- and biotopic conditions.     

Enzymes as reagents in the synthesis of peptides

The use of enzymes to catalyse peptide bond formation and for manipulating blocking groups during peptide synthesis is discussed. The history of solubility-controlled peptide condensations in the presence of proteolytic enzymes is traced. General techniques for obtaining improved yields of soluble condensation products are outlined along with special conditions which sometimes favour the enzymatic condensations of peptide fragments. Progress in the use of enzymes to manipulate blocking groups on α-amino groups, α-carboxyl groups, and on the sidechain functional groups of amino acid residues are examined. Some anticipated developments in the use of enzymes as reagents in peptide synthesis and semisynthesis are discussed.     

Influence of Group Size on the Success of Wolves Hunting Bison

An intriguing aspect of social foraging behaviour is that large groups are often no better at capturing prey than are small groups, a pattern that has been attributed to diminished cooperation (i.e., free riding) in large groups. Although this suggests the formation of large groups is unrelated to prey capture, little is known about cooperation in large groups that hunt hard-to-catch prey. Here, we used direct observations of Yellowstone wolves (Canis lupus) hunting their most formidable prey, bison (Bison bison), to test the hypothesis that large groups are more cooperative when hunting difficult prey. We quantified the relationship between capture success and wolf group size, and compared it to previously reported results for Yellowstone wolves hunting elk (Cervus elaphus), a prey that was, on average, 3 times easier to capture than bison. Whereas improvement in elk capture success levelled off at 2–6 wolves, bison capture success levelled off at 9–13 wolves with evidence that it continued to increase beyond 13 wolves. These results are consistent with the hypothesis that hunters in large groups are more cooperative when hunting more formidable prey. Improved ability to capture formidable prey could therefore promote the formation and maintenance of large predator groups, particularly among predators that specialize on such prey.     

Group connection and the number of males in female-philopatric animal groups

Previous studies have considered the equilibrium group size in gregarious animal species assuming isolated groups. Neighboring groups usually interact, which likely affects the equilibrium group size. Here I examine the possibility that the movements of solitary males between areas near neighboring groups cause the number of group males to increase in female-philopatric animal species when groups are connected. I hypothesized the following mechanisms. In habitats where groups are connected, solitary males move easily between areas near adjacent groups. Group males will accept one solitary male as a new member. Another solitary male migrates from an area near the group to an area near a neighboring group defended by relatively fewer group males. The model predicts that the number of group males increases through the hypothesized mechanisms when groups are connected if group males and solitary males do not cooperate effectively.     

A Cladistic Outline of the Eumycota

Abstract— A cladistic classification of fungi determined by a parsimony method with 21 terminal taxa and 51 characters is presented. Outgroup comparison with Oomycetes determined polarity assessments. The group Eumycota, including the traditional taxa Hyphochytriomycetes, Chytridio-mycetes, Zygomycetes, Ascomycetes and Basidiomycetes, is defined by two synapomorphies, molecular weight of 25S RNA, and chitin cell walls. Some groups are supported as monophyletic; Eumycota, Amastigomycota, Dicaryomycotina, Ascomycetes, Protobasidiomycetes, Basidiomycetes, Euascomy-cetidae, Hymenomycetidae and Homobasidiomycetales. The Hyphochytriomycota is the sister group to remaining groups. The Taphrinaceae and Saccharomycetaceae are more closely related to the Basidiomycetes than to any of the ascomycetous groups. In the absence of unique character sets groups such as the Mastigomycotina, Hemiascomycetes, Ustomycetes, Holobasidiomycetes, Heterobasidio-mycetes, Phragmobasidiomycetes and the Teliomycetes cannot be maintained and are abandoned as paraphyletic. Characters and terminal taxa used for the analysis are defined and discussed.     

On the complex formation of acridine dyes with DNA. VII. Dependence of the binding on the dye structure

The binding constants for the complex formation of more than twenty ring nitrogen-and amino-substituted acridine derivatives with calf thymas DNA were measured by a fluorescence method. DNA quenches the fluorescence of the aminoacridine dyes so long as both amino hydrogens are not substituted. These dyes show an enhancement of their fluorescence intensity in the presence of DNA. Typical representatives of both are proflavine and acridine orange derivatives, respectively. A discussion of steric and electronic influences of various substituents attached to the ring nitrogen and amino groups on the binding led to the concept of different conformations for intercalated acridines without amino groups and the aminoacridines. The electrostatic binding site of the former seems to be the positively charged ring nitrogen, while the binding sites in the aminoacridines are so located that the amino groups are directed towards the negatively charged DNA phosphates.     

Spatial summation of inhibitory influences in the eye of Limulus,and the mutual interaction of receptor units

The inhibitory influences exerted mutually among the receptor units (ommatidia) of the lateral eye of Limulus are additive. If two groups of receptors are illuminated together the total inhibition they exert on a "test receptor" near them (decrease in the frequency of its nerve impulse discharge in response to light) depends on the combined inhibitory influences exerted by the two groups. If the two groups are widely separated in the eye, their total inhibitory effect on the test receptor equals the sum of the inhibitory effects they each produce separately. If they are close enough together to interact, their effect when acting together is usually less than the sum of their separate effects, since each group inhibits the activity of the other and hence reduces its inhibitory influence. However, the test receptor, or a small group illuminated with it, may interact with the two groups and affect the net inhibitory action. A variety of quantitative effects have been observed for different configurations of three such groups of receptors. The activity of a population of n interacting elements is described by a set of n simultaneous equations, linear in the frequencies of the receptor elements involved. Applied to three interacting receptors or receptor groups equations are derived that account quantitatively for the variety of effects observed in the various experimental configurations of retinal illumination used.     

Regulatory mechanisms of cellular respiration; the role of soluble sulfhydryl groups as shown by the effect of sulfhydryl reagents on the respiration of sea urchin sperm

Oxidizing agents of sulfhydryl groups such as iodosobenzoate, alkylating agents such as iodoacetamide, and mercaptide-forming agents such as cadmium chloride, mercuric chloride, p-chloromercuribenzoate, sodium arsenite, and p-carboxyphenylarsine oxide, added in small concentrations to a suspension of sea urchin sperm produced an increase in respiration. When the concentration was increased there was an inhibition. These effects are explained by postulating the presence in the cells of two kinds of sulfhydryl groups: soluble sulfhydryl groups, which regulate cellular respiration, and fixed sulfhydryl groups, present in the protein moiety of enzymes. Small concentrations of sulfhydryl reagents combine only with the first, thus producing an increase in respiration; when the concentration is increased, the fixed sulfhydryl groups are also attacked and inhibition of respiration is the consequence. Other inhibitors of cell respiration, such as cyanide and urethanes, which do not combine with -SH groups, did not stimulate respiration in small concentration.