<informationTable xmlns="http://www.sec.gov/edgar/document/thirteenf/informationtable">		<infoTable>
			<nameOfIssuer>AQUABOUNTY TECHNOLOGIES INC</nameOfIssuer>
			<titleOfClass>COM NEW</titleOfClass>
			<cusip>03842K200</cusip>
			<value>2471</value>
			<shrsOrPrnAmt>
				<sshPrnamt>837554</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>837554</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>AQUABOUNTY TECHNOLOGIES INC</nameOfIssuer>
			<titleOfClass>COM NEW</titleOfClass>
			<cusip>03842K200</cusip>
			<value>19767</value>
			<shrsOrPrnAmt>
				<sshPrnamt>6700738</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<votingAuthority>
				<Sole>6700738</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>ENERGY TRANSFER EQUITY L P</nameOfIssuer>
			<titleOfClass>COM UT LTD PTN</titleOfClass>
			<cusip>29273V100</cusip>
			<value>12045</value>
			<shrsOrPrnAmt>
				<sshPrnamt>847650</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>847650</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>ENERGY TRANSFER PARTNERS LP</nameOfIssuer>
			<titleOfClass>UNIT LTD PRT INT</titleOfClass>
			<cusip>29278N103</cusip>
			<value>2868</value>
			<shrsOrPrnAmt>
				<sshPrnamt>176828</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>176828</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>ENTERPRISE PRODS PARTNERS L</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>293792107</cusip>
			<value>27803</value>
			<shrsOrPrnAmt>
				<sshPrnamt>1135734</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>1135734</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>FIBROCELL SCIENCE INC</nameOfIssuer>
			<titleOfClass>COM PAR</titleOfClass>
			<cusip>315721308</cusip>
			<value>3619</value>
			<shrsOrPrnAmt>
				<sshPrnamt>6133818</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>6133818</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>FIBROCELL SCIENCE INC</nameOfIssuer>
			<titleOfClass>COM PAR</titleOfClass>
			<cusip>315721308</cusip>
			<value>1259</value>
			<shrsOrPrnAmt>
				<sshPrnamt>2133595</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<votingAuthority>
				<Sole>2133595</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>HALOZYME THERAPEUTICS INC</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>40637H109</cusip>
			<value>344642</value>
			<shrsOrPrnAmt>
				<sshPrnamt>17592771</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>17592771</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>HISTOGENICS CORP</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>43358V109</cusip>
			<value>7399</value>
			<shrsOrPrnAmt>
				<sshPrnamt>2690570</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<votingAuthority>
				<Sole>2690570</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>INTREXON CORP</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>46122T102</cusip>
			<value>906504</value>
			<shrsOrPrnAmt>
				<sshPrnamt>59132705</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>59132705</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>NUSTAR ENERGY LP</nameOfIssuer>
			<titleOfClass>UNIT COM</titleOfClass>
			<cusip>67058H102</cusip>
			<value>2961</value>
			<shrsOrPrnAmt>
				<sshPrnamt>145200</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>145200</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>ORAGENICS INC</nameOfIssuer>
			<titleOfClass>COM PAR</titleOfClass>
			<cusip>684023302</cusip>
			<value>174</value>
			<shrsOrPrnAmt>
				<sshPrnamt>100056</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>100056</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>ORAGENICS INC</nameOfIssuer>
			<titleOfClass>COM PAR</titleOfClass>
			<cusip>684023302</cusip>
			<value>2520</value>
			<shrsOrPrnAmt>
				<sshPrnamt>1448110</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<votingAuthority>
				<Sole>1448110</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>OVASCIENCE INC</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>69014Q101</cusip>
			<value>81</value>
			<shrsOrPrnAmt>
				<sshPrnamt>100000</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>100000</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>OVASCIENCE INC</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>69014Q101</cusip>
			<value>222</value>
			<shrsOrPrnAmt>
				<sshPrnamt>273224</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<votingAuthority>
				<Sole>273224</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>PRECIPIO INC</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>74019L107</cusip>
			<value>730</value>
			<shrsOrPrnAmt>
				<sshPrnamt>1359121</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>1359121</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>SYNTHETIC BIOLOGICS INC</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>87164U102</cusip>
			<value>1154</value>
			<shrsOrPrnAmt>
				<sshPrnamt>3625000</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>3625000</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>SYNTHETIC BIOLOGICS INC</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>87164U102</cusip>
			<value>3061</value>
			<shrsOrPrnAmt>
				<sshPrnamt>9613268</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<votingAuthority>
				<Sole>9613268</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>TC PIPELINES LP</nameOfIssuer>
			<titleOfClass>UT COM LTD PRT</titleOfClass>
			<cusip>87233Q108</cusip>
			<value>3365</value>
			<shrsOrPrnAmt>
				<sshPrnamt>97000</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>97000</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>ZIOPHARM ONCOLOGY INC</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>98973P101</cusip>
			<value>38062</value>
			<shrsOrPrnAmt>
				<sshPrnamt>9709607</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>9709607</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
</informationTable>
