<informationTable xmlns="http://www.sec.gov/edgar/document/thirteenf/informationtable">		<infoTable>
			<nameOfIssuer>AMPLIPHI BIOSCIENCES CORP</nameOfIssuer>
			<titleOfClass>COM NEW</titleOfClass>
			<cusip>03211P202</cusip>
			<value>1592</value>
			<shrsOrPrnAmt>
				<sshPrnamt>400000</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>400000</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>AMPLIPHI BIOSCIENCES CORP</nameOfIssuer>
			<titleOfClass>COM NEW</titleOfClass>
			<cusip>03211P202</cusip>
			<value>3020</value>
			<shrsOrPrnAmt>
				<sshPrnamt>758788</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<votingAuthority>
				<Sole>758788</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>ENERGY TRANSFER PRTNRS L P</nameOfIssuer>
			<titleOfClass>UNIT LTD PARTN</titleOfClass>
			<cusip>29273R109</cusip>
			<value>2872</value>
			<shrsOrPrnAmt>
				<sshPrnamt>85135</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>85135</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>10338</value>
			<shrsOrPrnAmt>
				<sshPrnamt>752400</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>752400</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>ENTERPRISE PRODS PARTNERS L</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>293792107</cusip>
			<value>26497</value>
			<shrsOrPrnAmt>
				<sshPrnamt>1035834</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>1035834</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>FIBROCELL SCIENCE INC</nameOfIssuer>
			<titleOfClass>COM NEW</titleOfClass>
			<cusip>315721209</cusip>
			<value>46499</value>
			<shrsOrPrnAmt>
				<sshPrnamt>10219631</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>10219631</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>FIBROCELL SCIENCE INC</nameOfIssuer>
			<titleOfClass>COM NEW</titleOfClass>
			<cusip>315721209</cusip>
			<value>29124</value>
			<shrsOrPrnAmt>
				<sshPrnamt>6400783</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<votingAuthority>
				<Sole>6400783</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>GENESIS ENERGY L P</nameOfIssuer>
			<titleOfClass>UNIT LTD PARTN</titleOfClass>
			<cusip>371927104</cusip>
			<value>7973</value>
			<shrsOrPrnAmt>
				<sshPrnamt>217000</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>217000</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>HALOZYME THERAPEUTICS INC</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>40637H109</cusip>
			<value>343642</value>
			<shrsOrPrnAmt>
				<sshPrnamt>19829337</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>19829337</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>HISTOGENICS CORP</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>43358V109</cusip>
			<value>9417</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>1873741</value>
			<shrsOrPrnAmt>
				<sshPrnamt>62147301</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>62147301</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>MARTIN MIDSTREAM PRTNRS L P</nameOfIssuer>
			<titleOfClass>UNIT L P INT</titleOfClass>
			<cusip>573331105</cusip>
			<value>3077</value>
			<shrsOrPrnAmt>
				<sshPrnamt>141800</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>141800</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>NUSTAR ENERGY LP</nameOfIssuer>
			<titleOfClass>UNIT COM</titleOfClass>
			<cusip>67058H102</cusip>
			<value>4672</value>
			<shrsOrPrnAmt>
				<sshPrnamt>116500</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>116500</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>ORAGENICS INC</nameOfIssuer>
			<titleOfClass>COM NEW</titleOfClass>
			<cusip>684023203</cusip>
			<value>1501</value>
			<shrsOrPrnAmt>
				<sshPrnamt>1000555</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>1000555</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>ORAGENICS INC</nameOfIssuer>
			<titleOfClass>COM NEW</titleOfClass>
			<cusip>684023203</cusip>
			<value>18330</value>
			<shrsOrPrnAmt>
				<sshPrnamt>12219670</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>DFND</investmentDiscretion>
			<votingAuthority>
				<Sole>12219670</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>OVASCIENCE INC</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>69014Q101</cusip>
			<value>977</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>2669</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>SYNTHETIC BIOLOGICS INC</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>87164U102</cusip>
			<value>22014</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>SYNTHETIC BIOLOGICS INC</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>87164U102</cusip>
			<value>8301</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>TC PIPELINES LP</nameOfIssuer>
			<titleOfClass>UT COM LTD PRT</titleOfClass>
			<cusip>87233Q108</cusip>
			<value>4822</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>TRANSGENOMIC INC</nameOfIssuer>
			<titleOfClass>COM NEW</titleOfClass>
			<cusip>89365K305</cusip>
			<value>824</value>
			<shrsOrPrnAmt>
				<sshPrnamt>770490</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>770490</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
		<infoTable>
			<nameOfIssuer>ZIOPHARM ONCOLOGY INC</nameOfIssuer>
			<titleOfClass>COM</titleOfClass>
			<cusip>98973P101</cusip>
			<value>80544</value>
			<shrsOrPrnAmt>
				<sshPrnamt>9692403</sshPrnamt>
				<sshPrnamtType>SH</sshPrnamtType>
			</shrsOrPrnAmt>
			<investmentDiscretion>SOLE</investmentDiscretion>
			<votingAuthority>
				<Sole>9692403</Sole>
				<Shared>0</Shared>
				<None>0</None>
			</votingAuthority>
		</infoTable>
</informationTable>
